— Peter Griffin,Family Guy, "The Father, the Son, and the Holy Fonz"
Generally, if writers want to remove a character from their ensemble, they will either kill that character off or put him on a bus (or both) to explain their absence. Sufferers of Chuck Cunningham Syndrome, on the other hand, simply disappear into limbo. They will often be retconned right out of the story's history, while, of course, everyone still left on-screen will simply carry on as if Oceania has always been at war with Eastasia. This is sometimes caused by the writers gradually losing interest in the character and, without making a conscious decision to remove them, eventually forgetting about them entirely. More often, complications behind the scenes drive the decision to remove a character.
The Trope Namer is Chuck, who was actually Richie Cunningham's older brother for two seasons on Happy Days. Remember him? No?
In recent years, though, as media has become more meta, playful references to the ignominiously departed have become common, either as lampshades within the series itself or in parodies or satires of it.
A subtrope of Un-Person. Similar in spirit to The Other Darrin. Also see Out of Focus, when a character is gone but not quite forgotten; and Shoo Out the New Guy, who gets at least an excuse in the show for disappearing. Contrast with Remember the New Guy. For characters who are written out of the main story but are still hanging around in view, see Demoted to Extra. For characters who are specifically brought in for a one-shot purpose, see Long Lost Uncle Aesop. For characters that are given a reason for their departure and an on-screen send-off, see Put on a Bus. Compare Forgotten Fallen Friend and What Happened to the Mouse?. If a character appears in the pilot or very early episode of a show and then vanishes it may be a case of Early-Installment Weirdness. See also Absentee Actor. Present Absence is when this is averted.
This trope is only applicable to genuine members of the ensemble who would otherwise seem to be a little more permanent, not characters who appear out of nowhere for one or two episodes and vanish just as swiftly.
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Wendell the Baker for Cinnamon Toast Crunch used to have two other bakers named Bob and Quello/Quienno by some, but they disappeared for reasons unknown around the early '90s, and were never featured again.
McDonaldland and the vast cast of characters who once existed side-by-side with Ronald McDonald in McDonald's commercials were steadily eliminated from the 1970s onward, until only the "core cast" of Ronald, Grimace, Birdie, and Hamburglar remained. For awhile past 2000 now, McDonald's ads have only featured Ronald, and lately even he hasn't been seen terribly often.
The Burger King Kingdom was BK's answer to McDonaldland, and featured a colorful cast of characters including the milkshake-craving knight Sir Shakes-a-Lot, the picture-framed Burger Thing, the robotic Wizard of Fries, the skeptic Duke of Doubt, and The Burger King himself. They were phased out in favor of the BK Kids' Club in the late '80s, which itself disappeared shortly into the new millennium.
Cookie Crisp cereal had in its early marketing campaigns a bobby who chases after a bandit-masked thief and his bandit-masked dog. Eventually the thief vanished, followed promptly by the bobby, leaving just the dog (still wearing his bandit mask, oddly enough). Now the dog has completely vanished, having been replaced by a wolf named Chip (ironically the same name as the dog that preceded him).
Anime & Manga
Sailor Moon started ditching the entire supporting cast of the anime (including Usagi's parents and brother) sometime after the second season. All except Usagi's mother completely disappeared in the fifth and final season. As well as her best friend Naru and classmate Umino, whose final appearances are in the direct to DVD special Ami-chan no Hatsukoi at the end of the 4th season. They actually never appear in the 5th season and were already relegated to extras by the 3rd.
The manga actually ditches them even earlier.
Doctor Tofu from Ranma One Half, disappeared after the first third of the manga series because his role as Mr. Exposition for weird martial arts was adequately filled by Cologne, one of the Trickster Mentors in the series. Fanfic writers keep using him to provide a second opinion or comedy relief, though there was a joke in the fan community that he had fallen into an open sewer and died. This was only in the manga; he made minor appearances in the anime throughout the series.
Rumiko Takahashi's earlier manga Urusei Yatsura does this with Princess Kurama: after some time, she disappears altogether. She continues to get small cameos in the anime because of the crowd scenes.
"Lum's Stormtroopers" disappeared from the manga after Shutaro Mendo showed up, as he more or less filled their roles of being the rival to Ataru. The four became more significant in the anime.
Happens egregiously in the Slayers novels, more so the Special series. The most notable example is a mercenary named Lantz, who helps with the fight against Copy Rezo in lieu of Amelia in the third novel. He literally runs off, never to be heard of again. The only novel-exclusive character who is returned and remembered is the swordswoman Lemmy, who manages to make it to Amelia's side story and a radio drama. In the anime, similarly, Amelia's uncle, Christopher, doesn't get a single mention again after Slayers Next.
The Steel Saints from Saint Seiya, characters original to the anime's first season, completely disappeared before the 12 Zodiac Temples Arc. A common joke among the fandom was that they took the wrong plane from Japan to the Sanctuary.
Shamal from Katekyo Hitman Reborn!. He got a passing mention in the beginning of Future Arc and is never seen or mentioned anymore.
Several major characters in Medabots, such as Dr. Aki's niece Karin, never showed up in the second season. That said season was made specifically for the US market may have something to do with it.
In Onani Master Kurosawa, the unnamed younger sister of the protagonist appears in some boxes trying to talk to Kurosawa, only to be solemnly ignored (even by the author, after some chapters).
A character named Hanasaki appears. The characters become friends with him, he's around for some chapters, but after the Death-T arc, he disappears and is never mentioned again.
Miho Nosaka. She was a very minor character and Honda's love interest in the manga. She gets promoted as a main character in the first anime series, but is not in the second series Duel Monsters. But she was referenced in GX when she was listed among the missing Domino residents who are sent to the World of Darkness.
For a Hentai with so few characters, it's quite noticeable when Io Azuma in Moonlight Lady simply vanishes.
This happens a lot in car racing manga. In Wangan Midnight, literally dozens of minor characters, including Rumi Aikawa, Ma, Kochan, Yoshiaki Ishida, Harada, and Makoto Morishita, have been dropped without so much as a footnote.
Kimi Toudou, Kawaiiko and shameless Gold Digger from Fruits Basket. The last scene we see with her is her interrupting a love confession between Yuki Sohma and Machi Kuragi while looking for her missing hair brush. She never appears again. This is somewhat surprising as virtually every other minor character in the series makes some sort of appearance for a Cleaning Up Romantic Loose Ends chapter at the end. (Even Naohito Sakuragi, equal to Kimi in terms of importance, gets paired off with Motoko Minagawa [the Yuki Sohma Fan Club President] at the end.)
Klaus in Hayate the Combat Butler disappeared for around two hundred chapters with absolutely no explanation. Once or twice, it was helpfully noted that, yes, he's still alive.
In Mahou Sensei Negima!, Jack recounts the story of how Nagi saved his love interest, Queen Arika, a few years before Negi was born. No one has mentioned her since, and Negi hasn't asked. This also leads to a touch of Karma Houdini, since Arika has (evidently) never intervened to save her sister, her lover, or her 10-year-old son from fates worse than death.
The main character, Tamotsu, from the first Boku No Pico OVA is never seen or mentioned in the second or third ones.
Lampshaded in Dragon Ball Kai, when Krillin asks where she is Roshi mentions she went off in search of some treasure and he hasn't seen her since.
Interestingly, she was supposed to have shown up in the manga version of the Buu Saga's end, helping in gathering energy for the Genki Dama, but Toriyama forgot how to draw her. He made sure she showed up in the anime version.
Lin's puppy, Pel, from Fist of the North Star disappears some time during the Souther arc with no explanationnote only in the anime; it never even shows up in the manga. It shows up one last time in a later episode, only to never be mentioned again.
In From Eroica With Love, the first volume starts out with the main characters established as three psychic powered teens Sugar Plum, Leopard Solid and Caesar Gabriel. By the end of the first volume, they're no where to be seen and never heard from again, in favor of the actual interesting characters, Dorian Red Gloria and Klaus Heinz Von Dem Eberbach.
Because the movies are made before the actual series are released, certain characters are left out of the Pretty Cure All Stars movies. Among them, Eas/Setsuna in DX 1 and Seiren/Ellen and Ako in DX 3note It should be noted, though, that Setsuna and Ellen were evil at the time, while Ako hasn't been officially confirmed as Cure Muse, and was still busy keeping up with the silent protector disguise. Oddly enough, Itsuki and Yurido show up in DX 2 as brief cameos, despite Yuri being introduced three episodes after the week the movie was released. note Although Yuri is noticeably more OOC, not acting like a cold fish she started out as in series proper.
Atlee (aka Terra) after the writer/artist switch during Power Girl's solo series. She appeared in one panel of the first issue after the switch and was then never seen again. Especially noticeable as she had basically been Peeg's sidekick and was well liked by fans.
King Muskar XII of the fictional Balkan kingdom Syldavia was a major character in the The Adventures of Tintin story Tintin King Ottokars Sceptre (written in 1938), and ends up a close ally of Tintin. Yet he is completely absent for the post war stories dealing with Syldavia - in fact it is even unclear whether Syldavia is still a monarchy. Possibly a case of Reality Subtext: Muskar was based on King Leopold III of Belgium, who was forced to abdicate after World War II, and almost every Balkan kingdom except Greece was replaced by a republican form of government; although unlike the real-world Balkan states Syldavia did not become communist.
Famously done to Rikki in the Belgian comic epic Suske en Wiske (Spike And Suzy). Rikki was Wiske's brother, and a main character for the singular issue the comic was still called "Rikki En Wiske". He was never heard from again until after the author passed away, and the new writers decided to bring him back briefly after 254 (!) issues. The explanation? Rikki had gone out to buy shoes and somehow got stuck in Ruritania.
What exactly happened to Toxin in Marvel Comics is a topic that will likely never be resolved; even guys like Gravity and Sleepwalker get cameos now and then, but Toxin has plainly been abandoned entirely.
Toxin isn't the first symbiote character to disappear either, joining fellow heroic symbiote Hybrid and the female symbiote Donna/Scream.
In the current Venom series, the Toxin symbiote has a new host and is a villain now. Patrick Mulligan, its original host, died off panel. Hybrid and Scream were also killed off in this series.
In current Super Hero comics every time that either writer or status quo changes, most of the supporting cast and villains with exception of Ensemble Darkhorses (and sometimes even them) are put at risk of suffering from thiis. If there's no place for them in the hero's new life situation it can be justified. If they are gone because the writer didn't have an idea what to do with them, not so much.
When Brian Michael Bendis left Daredevil, the titular character had been imprisoned in one cell block with Kingpin, Owl and Jigsaw. New writer Ed Brubaker removed Jigsaw without any explanation.
Often happens to Spider-Man's supporting cast after all bigger changes of status quo.
Superman's post-Crisis supporting cast is notable because they were built up over such a long stretch of time, and then summarily jettisoned in 1999 when the Dan Jurgens/Louise Simonson era ended. Perry White's family, Bibbo and the other characters from Suicide Slum and the Bottle City characters introduced during the '90s all vanished abruptly never to return and characters like Emil Hamilton got thrust deep into the background overnight.
One of the most popular features of Bill Messner-Loebs' run on Flash was the large supporting cast — they even carried the book without Wally for a couple of issues. When Mark Waid took over, all of these characters except Linda Park faded into the distant background. Piper showed up sometimes, and Chunk got the occasional cameo, but the new "Flash family" that Waid proceeded to assemble replaced everyone else (including Wally's real family). Waid's run was wildly successful, but longtime readers still regret the loss of those characters.
In the 90s, Lex Luthor was a prominent businessman who was ruthless but maintained occasional Pet the Dog moments. Among these was the fact that he had an infant daughter named Lena Luthor, who he loved very deeply but nonetheless got roped into his life as a supervillain against his wishes. After 2004 though, Luthor became a Mad Scientist for a little while and with Dan Didio and Geoff Johns at the helm of the DC, his character was sent into a different direction. In the midst it all, Lena just disappeared and it was never explained what happened to her or where she is now. At the moment, Lex Luthor's only biological child is Superboy.
Her disappearance was eventually explained. As a result of the Cosmic Retcons that took place during Infinite Crisis, Lena was Retconned into being Lex's younger sister (which she had been Pre-COIE) rather than his child. Lena's daughter Lori subsequently became a prominent supporting character in Superboy.
Happens with ridiculous regularity in the X-Men books, especially once Xavier's Institute became a full-fledged school with a student body beyond the active team members, only getting worse after the "Decimation" event reduced the mutant population to around 200 (prompting the X-Men to try to get literally every mutant on Earth to live at the X-Mansion and, later, Utopia). Whenever a new writer takes over, you can count on at least half the extended cast quietly vanishing. Sometimes a later writer will remember them and either mention where they got off to or reveal that they've been there all along never really doing anything.
Dana Drake, the stepmother of Tim Drake, the third Robin, is a particularly egregious example. When Tim's father Jack was killed off in Identity Crisis, it was done so Tim could be tied more closely to Bruce, who would formally adopt him. The problem is, though, that Jack had remarried to Dana, who'd been a major supporting character all through Robin's own series. Dana would have a mental breakdown over Jack's death and be sent to a sanitarium to recover... In Bludhaven, which would soon be completely destroyed in Infinite Crisis. One could assume Dana died along with everybody else in Bludhaven, but it was never explicitly stated she did. Instead, she has simply never been mentioned again. Evidently, DC editors wanted to get rid of her, but realized having Tim Angst over losing both his father and stepmother in 2 close together yet completely isolated incidents was too much even for DC. She'd be a Forgotten Fallen Friend except it was never confirmed she'd fallen. So instead, she's this trope.
The Impulse supporting cast soon vanished after his book ended, most notably Bart Allen's best friend Preston and love interest Carol. Much to fans' displeasure, one line in Geoff Johns' Teen Titans had Bart suggest it was Wonder Girl who got him to like girls, rather than mentioning Carol or even Arrowette (another crush of his). Bart's pet dog Dox was also never seen again or mentioned by any later writers.
Holly Robinson was one of Catwoman's prominent supporting cast members, even temporarily taking on the codename for an arc in the One Year Later era. However, after the "Countdown" event, Holly vanished and was never seen again in the Batman universe. A later throwaway line about the character suggests that she moved elsewhere after receiving a huge sum of stolen money from Hush's fortune. This is in no small part because of the sorry reputation her creator, Frank Miller, picked up over the years–the makers of The Dark Knight Rises even went so far as to create a similar character called Jen to avoid having to forward any money to Miller.
Post-CrisisWonder Woman's adoptive mother Julia Kapatelis. When George Perez was removed from the series, she vanished for some time. Her daughter Vanessa would also disappear, until she was retooled as a new Silver Swan.
This is pretty much true for most Wonder Woman characters not created by Perez or the original Golden Age creators. There are tons of love interests, supporting cast members and villains who simply never appeared again after their respective creator left the series. The few exceptions would be characters like Phillipus and Artemis, and even they seem to have been dropped as of the New 52 revamp.
A mid-story issue of the Super Mario Adventures comic strip, which ran in Nintendo Power during 1992, featured this. Toad uses a Cape Feather to fly up to a pipe sticking out of a cloud (allegedly the one Mario and Luigi entered at the beginning of the story to unknowingly wind up in Dinosaur Land), and gets "help" - which is actually Bowser's Koopa Troop in disguise (the cloud was actually an airship of sorts in disguise). After the Princess gets kidnapped, Toad is shown being held hostage by two Koopas, delivers one line about the Koopas "taking control of the Mushroom Kingdom", and is then never seen or mentioned again for the remainder of the comic (So they just left Toad in the Koopa Castle dungeons?).
In the Star Wars: Tales of the Jedi comics, main characters included Nomi and Vima Sunrider, the latter of which was going to be in Knights of the Old Republic. However, due to unclear trademark restrictions involving the name "Sunrider" (speculated to be from either a brand of convertible tops for Jeeps or some kind of corporation that makes herbal products, neither of which is very easy to mistake for a comic character), the characters stopped appearing at all in the Star Wars Expanded Universe, aside from an accidental anecdote in the first KOTOR game and an item description that didn't mention the last name in the second. However, Lucasfilm Licensing has apparently gotten past the worst of it, and can now create products and media featuring the characters, provided the name "Sunrider" isn't mentioned on the external packaging, and a book about Nomi Sunrider was due out in 2011. (See Wookiepedia.) For whatever reason, however, the book was cancelled.
Blackhawk: The early stories in the 1940s featured three squadron members named Zeg (Polish), Boris (Russian) and Baker (English). They all vanished without trace after their initial appearances.
Boris DID return briefly in the short-lived mid-1970s revival.
When the Micronauts began appearing starting in 1996 issues of Cable, not only was their reappearance due to a very apparent retcon, but no mention was made of Acroyear or Huntarr. Acroyear's absence is most likely due to the fact that Marvel no longer has the rights to any of the Micronaut characters derived from the old-school toyline. It doesn't explain why Huntarr is not there, as he was created by Marvel writer Bill Mantlo.
Wayne's in Pain, a character put into The Bash Street Kids (a comic strip in the Anthology ComicThe Beano) after a Blue Peter competition, disappeared after being in the strip for only a short while.
A number of characters from the Sonic the Hedgehog series have disappeared from the face of the Earth, especially if they weren't mainstream Sega-based characters or part of the Saturday Morning series. However, one bad example of this is Dulcy Dragon, a character from the second season of the Saturday Morning cartoon. She had a few roles up until issue 50 before appearing in a set of back stories along with Amy Rose. Beyond one last appearance in the early 100s, Dulcy has rarely, if ever, been seen again.
However, Ian Flynn's run has revived a number of characters and pulled them out of this hole, including Scratch, Grounder and Coconuts, and obscure, early issue characters such as Larry Lynx and Harvey Who.
On the other hand, thanks to a heaping dose of Screwed by the Lawyers, a large majority of the non-SEGA-approved characters (re: those created by former head writer Ken Penders) have disappeared due to Cosmic Retcon. However, being what the comic is, the entire thing is lampshaded greatly.
A side-effect of being such a Long Runner, Archie Comics have introduced several characters who never appeared after a few issues. Sometimes their absence is explainable, like the alien characters who have landed and vanished soon after. But then we have cases like Betty's older brother and sister, who have been recurring characters in Little Archie but are never mentioned in any of the teen or adult Archie stories.
Wiccan of the Young Avengers originally had two younger brothers, who have since fallen off the face of the earth.
Marvel Boy (formerly the Protector) had a girlfriend named Annie while he was a member of the Avengers. They had a very close relationship, and there were even some dangling plot threads concerning their relationship when Bendis left the book. Then came the second volume of Young Avengers, where Marvel Boy was shown shacking up with Kate Bishop without even a single mention of Annie.
This was eventually explained. Marvel Boy dumped Annie at some point between The Avengers and Young Avengers, leading to her eventual return as an Ax-CrazyWoman Scorned.
DC attempted to retool the Hawk and Dove concept in the late '90s with a book starring two winged humans; an army brat named Sasha, and a laid-back rock musician named Wiley. Due to the In Name Only nature of the characters and the lackluster reception, the two quickly vanished, not even to be brought out as cannon fodder in any events. For all intents and purposes, the two characters seemed to have never existed.
Occasionally occurs in fanfiction, usually to minor characters or Scrappies. With the nature of fanfiction though, it's much more common for the author to kill off the unwanted character or turn them into a horrible bastard. If the author is nice though, they'll usually put the character on a bus and/or Hand Wave their disappearance.
In the Disney movie A Goofy Movie, Roxanne is shown to be Goofy's son Max's love interest. In the sequel, An Extremely Goofy Movie, Roxanne and her best friend Stacey (Max's friend Bobby's love interest) never appear and are not mentioned, despite all the trouble Max went on that summer. Roxanne does appear in an episode of House of Mouse, though. Meanwhile, A Goofy Movie itself removed Pete's wife, Peg and PJ's sister, Pistol along with both the family pets, Chainsaw and Waffles, from Goof Troop, without even a passing mention of any of them in either movie, and with a line in the sequel that explicitly proves Pistol's not around anymore.
In the sequel of the 2007 Transformers the Autobot twins, Skids and Mudflap have this happen. After the fight with Devastator, you don't see them again for the rest of the film. They don't even return in Dark of the Moon.
They do return in the comic adaptation and novelization for "Dark of the Moon"...and get killed alongside Ironhide.
The original Transformers: The Movie does this to some of the surviving cast members up to that point, as nearly anyone who didn't die or was implicitly shown to have survived is never mentioned again.
Shortly after Unicron transforms Megatron into Galvatron, Skywarp and Bombshell are transformed into the identical "Cyclonus and his Armada", however, the "Armada" (which is just one guy) is never seen or mentioned after this scene. It is disputed who got reformatted into Cyclonus and who into the Armada. Bombshell is the one shown in front and Skywarp further at the back so it is considered that Bombshell got formatted into Cyclonus however. Skywarp is the major character and much more loyal to Megatron (Bombshell and the other insecticons consider them seperate from the other Decepticons) and has the personality of becoming Galvatron's/Megatron's new Number Two.
If you look closely, whenever Snarl is present, one of the other Dinobots is missing. And the script even refers to "the four Dinobots". It's like the entire production team thought there were only four of them and couldn't decide which four there were.
Nightcrawler was a major character and love interest for Storm in X2: X-Men United, but didn't even appear in the third movie because actor Alan Cumming found the make-up and prosthetic process grueling and refused to return to it without Bryan Singer. Cumming can be seen in the behind-the-scenes footage for X2 already stating that he never wants to go through the ordeal again. The video game based on the films which takes place between 2 and 3 explains that Nightcrawler, a peaceful man, went abroad to distance himself from the X-Men's violent lifestyle.
Dr. Dolittle: Rodney the guinea pig is nowhere to be found come the sequel, probably because his voice actor, Chris Rock, declined to return. While Rodney may likely have died of age by Dr. Dolittle 2, this is never addressed at any point.
In the early Olsen Banden movies, Kjeld and Yvonne had two children: A son Břrge and a smaller daughter. As the series went on Břrge became an important regular while his sister vanished into thin air.
At least in the Norwegian versions, Kjell had two sons and a baby daughter in the first movie, and while the middle son Basse becomes a regular character, the other two have disappeared completely by the second one. Likewise, Benny ends up fathering a kid during the first movie, but both kid and fiance are never again referred to, and the only supporting cast member to reappear is Hansen the bartender. After movie 2, he's gone too.
In the animated version of Charlottes Web Jeffrey the gosling, Wilbur's best friend besides Charlotte, is never seen again after he attempts to join Wilbur, Charlotte, and Templeton in the crate and is taken out.
Anamaria is never seen or heard from again after the first Pirates of the Caribbean movie. Interestingly, the cast was told in Dead Man's Chest that Anamaria would appear at the ending of the film, so the shock and surprise of Captain Barbossa greeting them was genuine.
In Pocahontas: Journey to a New World, Thomas and Wiggins do not appear
In The NeverEnding Story III, Atreyu — who the co-protagonist of the first film and a major character as Bastian's best friend in the second — is nowhere to be seen. The very noticeable actor changes for both Atreyu and Bastian between each film create a lot of dissonance anyway.
American Pie and American Pie 2 center around four friends; Jim, Kevin, Finch, and Oz. In American Wedding, Oz is completely left out. You'd think they'd at least mention why one of Jim's best friends didn't attend his wedding. He returns for Reunion though.
In Eddie and the Cruisers, Frank Ridgeway plays a key role in the band and the story. When the sequel comes out, there's no mention of Ridgeway at all. They even go so far as to replace Frank's image with Sal in recycled footage from the first film.
At the end of Legally Blonde, Elle becomes best friends with Vivian Kensington, her rival for her boyfriend. However, in the sequel, Vivian is never even mentioned.
Shenzi, Banzai and Ed failed to appear as well, although they are mentioned to have fled from Pride Lands following the first film. They also made several appearences in the 1995 Timon & Pumbaa series.
In the Direct-to-Video sequels to An American Tail, Bridget, the love interest of Fievel's older friend Tony Toponi, vanishes without even a mention and Tony starts lusting after other women. This could possibly be because, similarly to The Lion King 2 example, Bridget's voice actress was terminally ill when the movies were made and died soon after (for their faults, the 3rd and 4th films did manage to get most of the original voice talents from the first two movies). It could also have been because the writers wanted Tony to be single so he could interact with Fievel more.
In Batman Returns, Catwoman, Batman's love interest and villain throughout most of the movie, is last seen on the roof of a building before the movie ends, and is never seen again in the two subsequent films (and is only mentioned once, and in a subtle way, when Chase Meridian says "Or do I need skintight vinyl and a whip?"). Michelle Pfeiffer was meant to get her own film as Catwoman, but the project fell into Development Hell and eventually crawled out in 2004 with Halle Berry as the star and nothing to do with the Burton films.
According to Batman Wikia, Catwoman was suppose to appear in the then planned second sequel directed by Tim Burton, but Warner Bros considered Burton’s dark toned-movies to be difficult to sell to young audiences, so the project was then passed to Schumacher. We know what happen.
Crabbe disappears from Harry Potter and the Deathly Hallows Part 2, when he always appeared alongside Goyle in all of the first six films. Although the filmmakers had a reason for cutting him out (his actor was arrested for drug possession), no mention is given to him at all, Harry never asks where he is, and Malfoy doesn't seem to notice, as he specifically gets Goyle and Blaise Zabini (another Slytherin ally in the books) when he Apparates into the dungeons. Crabbe was supposed to die in this movie too, but due to the character omission they killed off Goyle instead.
Parvati Patil, who does not appear alongside Padma in the last film (who was seen less in the series than Parvati).
Viktor Krum, Rita Skeeter, Cornelius Fudge and Buckbeak, among others. While they're not exactly main characters in the books after their main plotlines end, they do appear in later books. In the films, on the other hand, they're not even mentioned after they've gone.
Some of the Hogwarts ghosts didn't make it past the first film. Nearly Headless Nick managed to stick around a little bit longer and was last seen in the second film. Moaning Myrtle disappears after the fourth film. Colin Creevey has a sizable role in the second film and is then never seen again. He's sort-of replaced by Canon Foreigner Nigel. Madam Hooch is only in the first movie. The Fat Lady is never seen after the third movie and that appearance was a case of The Other Darrin.
What's particularly odd about the Colin/Nigel situation is that when there are pictures of Nigel in companion media, he's often referred to as 'Colin Creevey'.
Blade gave us Karen Jenson, a haematologist who develops a biochemical weapon against vampires and even finds a freakin' cure for vampirism. The movie ends on the note that, if she wants to be useful, she'll have to make Blade a better serum to suppress his bloodthirst. She never shows up or is mentioned in the sequels, but Blade doesn't have any serum-related problems (so presumably she did make him a better one), and other characters are mentioned as being cured of vampirism.
In the first Men in Black movie we're told that K was in love with his old girlfriend throughout his career and his original partner was D. In the third movie, J time travels back to the early years of K's career. K is shown to be romantically interested in O and there's no mention of his old girlfriend or D.
In High School Musical, during the "Stick to the Status Quo" musical number, three characters decide to follow after Troy and confess their Hidden Depths: a member of the school's basketball team bakes, a smart girl dances hip-hop, and a skater boy plays the cello. While the first two, Zeke Baylor and Martha Cox, become major supporting characters, the skater boy is never seen or mentioned again once the song is done.
The Dark Knight Rises: Due to Heath Ledger'sdeath, the Joker is not released by Bane with all of Gotham's other prisoners. People are 90% certain that he would have played Scarecrow's role in the plot, were the actor still alive.
The Police Academy franchise has a nasty case of the syndrome with characters disappearing between each of the sequels:
Their First Assignment: Cadet Leslie Barbara, Cadet Karen Thompson, and Cadet George Martín.
Back in Training: Capt. Pete Lassard and Sgt. Vinnie Schtulman.
Citizens on Patrol: Cmdnt. Mauser, Sgt. Kyle Blankes, Mrs. Fackler, Cadet Hedges, and Cadet Karen Adams.
Mission to Moscow: Sgt. Nick Lassard, Sgt. Laverne Hooks, Sgt. Douglas Fackler, Lt. Proctor, Lt. Moses Hightower, and Commissioner Henry Hurst.
Although this may yet change, Thanos's servant, The Other, who serves as a means of communication between him and Loki to keep his master's identity a secret until the post credits scene in The Avengers, has not yet been listed in the cast of characters of Guardians of the Galaxy, but at least three of Thanos's other servants who have not appeared in any previous films are. It is, however, possible that his true identity could be Ronan the Accuser.
A Series of Unfortunate Events: The wart faced man from Olaf's troupe disappears after the 1st book and is never mentioned again. Also didn't reappear in the movie that was made 5 years later.
Animorphs: Hey, remember Mertil, the Andalite that had also survived Elfangor's ship's crash and had been living on Earth for the entire war? Remember how he was found by the kids and decided to remain in hiding? Or maybe you don't, because he was only in one book. Having another Andalite on board would've been very useful for the kids. Even if Mertil didn't join the kids for his own reasons, it would've been nice for him to get another mention, seeing as an Andalite war hero living on Earth is kind of a big deal.
In "Cheaper By the Dozen", Mary, the second eldest child dies at age 6. This isn't mentioned in the book. She simply stops appearing.
In The Baby-Sitters Club, this was the eventual fate of most of the girls' non-club friends, fuelling speculation that the girls were disturbingly cult-like...The major exceptions are Laine Cummings, Stacey's on-again, off-again best friend from New York, and Sunny Winslow, Dawn's Troubled, but Cute best friend from California. But Sunny started her own baby-sitting club, anyway, so she doesn't really count.
Don Quixote: In Chapter I, Part I, Cervantes mentions the people who lived in Don Quixote’s house: his niece, his housekeeper and a lad who helps them with the field and the marketplace... we'll never see or hear anything about that lad again. Obviously, Cervantes had completely forgotten about this character, and didn't want to write him even in the Second Part of the novel, but in his defense, one of Don Quixote's themes is about how silly it is to detect errors of continuity in a silly fictional tale...
Near the end of Frankenstein Victor notes that, with his wife, baby brother and best friend murdered and his father dead from grief, he has lost every important person left in his life. ...Except wait, didn't he have another brother named Ernest? Did the monster get him too?
Rifleman, mentor to and important ally of Stile's in the first Apprentice Adept trilogy. When the second trilogy starts up, he's nowhere to be found or mentioned.
Tobias Gregson, the only member of the main cast from the first Sherlock Holmes story, A Study in Scarlet, to never become a regular. There are mentions of "Gregsons" in later stories, but they are very few, only sharp eyes will catch them, and there is no indication that any of them refer to Tobias.
In the Artemis Fowl series, Doodah Day. At the end of Lost Colony, he is mentioned as having started working as a private detective along with Mulch Diggums. The Time Paradox takes place mostly in the past, so it's understandable that he wouldn't appear, but Mulch is actively involved in The Atlantis Complex and not only does he not seem to be working as a detective, there is absolutely no mention of what Doodah is doing.
Minerva Paradizo. At the end of book 5, she is stated to have spent 3 years obsessing over Artemis, waiting for him to return, and she was set up as a very obvious Love Interest. Two books later, and she hasn't been mentioned once since then.
The 19th-century penny dreadful Varney the Vampire began with three children in the Bannerworth family — Henry, Flora, and George — but George is never mentioned again after Chapter 36.
The Sisterhood Series by Fern Michaels: This has happened to some characters. Private Detective (former FBI agent) Mark Lane seems to pretty much vanish off the face of the Earth by the book Final Justice. It might be due to the fact that he acts as a source of information for Jack Emery, who by then is getting information before Lane does, and Jack doesn't really need him anymore!
There were two sequels to Harriet the Spy. Sport and Janie, Harriet's best friends, get not a single mention in either of them.
As the Moomimtroll series progresses, the Moomins keep acquiring new house-guests, until the second-to-last novel Moomimpappa at Sea, where, with the exception of Little My, they all vanish without a word. Particularly jarring is the Snork Maiden, who up until this point has been Mooomintroll's G-rated love interest.
Happens to the wizard Radagast the Brown in The Lord of the Rings. Messengers are sent to his house mid-way through the first book, but find it deserted. His absence is never explained, and he is never mentioned again. When asked about this in a letter, Tolkien said that even he wasn't sure of Radagast's fate.
Has no qualms about having characters cease to exist once their purpose has been served, even though its high body count means you'd think someone could spare a bullet for any of them. Worse, many of them were last seen in situations where death is likely but not a given. In some circles, this is called "Behroozing," after Behrooz Araz, a character who vanished in such a manner. Most notably:
The unnamed Eastern European assassin from the first half of season 1, who pretends to be an American photographer named Martin Belkin. The assassin plays a major role in the first half of the season, as he gets a face transplant and attempts to kill Palmer at a rally in downtown Los Angeles. After he is foiled by Jack Bauer, he flees and is never seen again (even though the other assassin hired to off Palmer, Mandy, is seen in several more episodes in different seasons afterwards).
Lynne Kresge (an assistant to President Palmer) is pushed down a flight of stairs late in the second season. Even though she's badly injured, she doesn't seem to be in danger of dying (and she's loaded into an ambulance, knowing damaging information about Mike Novick). Strangely, she's never referenced again, even when Palmer returns to the White House and talks at length with Novick.
John Keeler and Wayne Palmer both exited the show this way. While a reference to Wayne dying is made in a prop newspaper from Redemption (albeit, never shown on-screen), Keeler is never mentioned again after being listed in critical condition after Air Force One crashes. This actually has a justification—the writers were explicitly told that they weren't allowed to kill off a sitting president on-screen. Presumably since Daniels had already taken over and served out the rest of Wayne's term, it was okay for them to let it be known that Wayne was dead, and David Palmer's death happened long after he left office. This may not have been restricted to United States presidents, either. In Season 8, Omar Hassan, the president of a fictional Middle Eastern nation, is killed, but his death is not actually shown on screen; while CTU is trying to rescue him, the internet video feed that the terrorists have set up is shown, and then when Jack gets there and finds Hassan's dead body and realizes that the video was pre-taped, we aren't shown the conclusion.
Karen Hayes, the wife of long running character Bill Buchanan, who is sort of put on a bus with her husband at the end of Season 6 as they are both forced to resign. However, Bill is a main character for most of Season 7 and his wife is never mentioned not even after his death. Her not being mentioned is partly justified in that Bill spent most of his time in the field where there was less time for chit-chat than when he co-ordinated from CTU.
Daniel Dae Kim played a field agent in the first few seasons that was one of Jack's earliest field partners over the course of the show. In the second half of season 3 he worked with Jack and Chase in their attempt to capture that season's Big Bad Stephen Saunders, but after a botched attempt he completely disappeared and was never seen or heard from again, thanks in part to Kim moving over to LOST right around the time those episodes aired.
Dennis Ryland was a prominent character for the first three seasons of the show (though he did experience a brief absence), first as the head of NTAC, then as a notably more antagonistic character in a higher level of government. However, he disappeared entirely, and without explanation, for the show's fourth and final season, with only a single, fleeting reference being made to him as one of the people who exploited Isabelle Tyler. This despite the fact that the project he was working on (the development of promicin-enhanced soldiers) was at its height at the end of the third season.
Similarly, Nina Jarvis, the head of NTAC for the second and third seasons, disappeared with no further mention in the fourth season, her role being filled by new character Meghan Doyle. It can be presumed she quit, though no explanation is given.
Then there's Diana's boyfriend, Ben, introduced near the end of the third season and disappearing mid-way through the fourth with no further mention. The implication is that they broke up, though this is quite surprising considering how well they'd been doing as a couple... and the fact that this contradicts one of Maia's infallible prophecies.
All My Children: In a 1970 episode of this soap, a teen named Bobby Martin went up to his family's attic to wax his skis. The actor was then abruptly fired and so Bobby was never seen again. Decades later, the show lampshaded this by having a character go into the same attic and find a skeleton with a pair of skis, wearing a ski hat with "Bobby" on it - a comedic example of a Bus Crash.
The Andy Griffith Show: Jack Burns' character of Warren Ferguson, who was brought in to replace Barney Fife as Mayberry's overzealous deputy. He lasted one season before being quietly dropped from the show and never mentioned again. (Even the '80s Reunion Movie forgot about him.) Another example would be Ellie Walker, the town pharmacist and Andy's first-season girlfriend.
Angel: Detective Kate Lockley, Angel's Agent Mulder-esque contact with the LAPD in this series, made her last appearance fairly early in the series, when she hit a Despair Event Horizon and was barely saved from a suicide attempt by Angel. She completely vanished from the story after that, partly because the actress moved on to Law & Order and partly because the show had already begun to drop the idea of Angel as an Occult Detective who'd need to work with the police in favor of a broader Urban Fantasy story. She did return, though, in the comic-book series that continued the storyline after the show ended.
Are You Being Served?: Had a few regular characters vanish without mention, with the most memorable being Mr. Grainger and Mr. Lucas (actor left to pursue other interests).
Babylon 5: G'Kar's assistant Na'Toth only appeared twice in the second season (after an unsuccessful recasting and didn't appear at all in that season's second half. A third season episode mentioned that she'd been on Narn when the planet was bombed into submission by the Centauri and was presumed dead. Finally in an season 5 she reappeared for one episode as a P.O.W. on Centauri Prime and was sneaked onto a transport home. Interestingly, G'Kar's first assistant Ko'Dath also disappeared off-screen (though this was explicitly mentioned on screen as death due to an "unfortunate airlock accident"). Is it any wonder why G'Kar becomes something of a loner for most of the series?
Barney Miller: Detectives could be dropped with little or no explanation. One notable example was Eric Dorsey, the abrasive newcomer introduced in the last season. When they knew for certain it was the last season he was dropped in the buildup to the Series Finale.
Battlestar Galactica (Classic): In the original show, Commander Adama's daughter/Apollo's sister Athena vanishes without explanation after the episode "Greetings from Earth: Part I."
Boxey in the reimagined show completely vanished without explanation after a relatively prominent role in the miniseries and a smaller scene in one regular episode. He was meant to be a kid that the pilots had adopted, but the writers couldn't come up with uses for his character. It could be justified as Commander Adama may have decided that a military ship in a time of war was no place for a child and sent him to live with a foster family in The Fleet. It should be noted that he was featured in several episodes in Season One, but all of his scenes were cut out due to timing constraints or pacing.
His photo does appear on the Wall of Remembrance in later seasons, implying his death sometime between Ragnar Anchorage and Earth. It gets expanded upon in one of the tie-in novels, which has him living in fosterage in the fleet, and getting fatally shot helping Helo and Starbuck stop an attack by an apocalyptic religious cult in the fleet (the novel also pins down his death as occurring during Commander Fisk's tenure in command of the Pegasus).
Prominent Quorum members such as Marshall Bagot and Sarah Porter simply disappear after the Second Season. It is possible that they died during the explosion of Cloud Nine or the Cylon Occupation or were simply not voted back into office in the new administration and thus lost their relevance, but it is never addressed.
Another character, Bulldog, was given an entire episode's focus when he was introduced, then was never heard from or mentioned again. The story is that he was intended to be a recurring character afterwards, but the actor playing him couldn't work out his schedule to fit the show. Word Of God says in the podcast for Bulldog's lone episode, "Hero", that they decided to wrap up the character's arc within a single episode because Carl Lumbly was an "expensive actor".
Becker: Bob was said to be "on vacation" in the first episode of Season 6, and never returned.
Has new upstairs neighbor Alicia, the driving force behind a season two episode. She's never seen or heard from again, although one assumes she still lives upstairs (unless Sheldon managed to get her evicted for being too noisy). It's noted in-show that Alicia gets a part on a TV show, so it's possible she moved on, as well.
Similarly, Leonard gets a love interest, Dr. Stephanie Barnett (Sara Rue) in Season 2. Fearing they're moving too fast, he tries to break up, but she keeps luring him back with sex. At the end of their third episode, he heads off for another booty call. Presumably he grew a spine between that and the next episode, when she's just gone.
In Season 6, the character Stewert disapears rather abruptly during a party at his comicbook shop, to be replaced by a new love interest for Raj. Stewert is not even mentioned again for the rest of the season, which is especially odd given he was living in Raj's spare bedroom.
Percy, of Blackadder fame, was completely excised from canon. Tim McInnerny, who played Percy in the first two series, didn't want to be typecast playing a buffoon, so he played different characters (Topper in Series 3 and Darling for all other appearances) afterward, and Percy was subsequently replaced in the show's main Comic Trio by George. His lack of appearances after series two can be justified at least due to the fact that each series takes place in a different time period, and one can assume that the Percy of Series 2 never had any descendents. Not as much for specials that harken back to the timeline pre-Series 3 however, which don't have him get a single mention or appearance even though other returning characters have.
The Bob Newhart Show: The first season had Margaret Hoover, a neighbor in the Hartleys' apartment building and friend of Emily's. She appeared in a handful of episodes before being quietly dropped.
During the first season, Jonathan Adams plays Dr. Goodman, the head of the Jeffersonian Institute, who is Bones's direct superior and takes an active role in many of the cases. In the first episode of season two, Cam is head of forensics, and Goodman is said to be on a "two month sabbatical"; four years later, he's yet to be seen or mentioned again. (Word Of God is that he may eventually pop up in guest appearances, however.)
This trope was even applied retroactively, as Dr. Goodman is never even mentioned during a flashback episode set before the pilot.
This also happens with a restaurant owner, including the restaurant. In the first season, the main characters frequent a restaurant where the quirky owner knows better than you want you want/need, so it's better to not order and just let him bring you whatever he feels is best, but in season 2 they suddenly start going to a diner instead and the restaurant is never mentioned again. Of course, they could have just decided they liked the diner better, but the switch is never explained in any way, even though Booth seemed to be on quite friendly terms with the owner of the restaurant.
Early episodes offer a possible explanation: the owner complained about the Squints bringing photos of crime scenes and bodies to the restaurant with the threat of not allowing them back if they kept it up. However, there was nothing confirming this as the reason they stopped going.
In one early episode, we see Topanga's older sister, Nebula. She is never referred to again and indeed Topanga is later stated to be an only child.
In earlier seasons, Shawn had at least two siblings before Jack came into the picture. There was an older brother who Cory caught stealing or something on video, and an older sister he called after Cory had him help straighten his hair.
Minkus, a recurring character from the first season, also disappears without a trace. Later, when the show became more meta, they had him return for their high school graduation, pointing off-stage and saying that all his classes had been down the other hallway. The kids wave down the hall, shouting hello to their old teacher Mr. Turner, who had also been Chucked. (Ironically, the actor playing Minkus was one of the three Torkelsons to survive the Re Tool into Almost Home).
Cory's sister, Morgan, almost got the Chuck treatment. She disappears entirely at the end of season 2. Her character is brought back in the middle of season 3 (as a different actress), and remarks, on her first appearance, "That was the longest time out I've ever had!"
Tiger, the family dog. Gets a Lampshade Hanging in The Brady Bunch Movie. (A case of Actor Existence Failure according to Barry Williams; the dog was run over by a car early in the first season.)
For that matter, the girls' cat, Fluffy, didn't make it past the pilot episode.
When Breaking In was (briefly) Un-Cancelled, team member Josh vanished without explanation. There was a minor handwave for another major character who was not technically a team member, Dutch, disappearing at the same time.
The first series features pretty secretary Angie as a main character in all episodes. She vanishes without a trace from series 2 onwards, replaced with a brand new secretary, Julie, who is merrily treated as if she's been there since the beginning by all the other staff.
Of course, the whole thing did turn out to be a dream, so...
British ensemble dramas are rather notorious for this, with regular characters vanishing in between seasons. Casualty and Holby City were noted for it in the days before they were on all year round. (Between the eighth and ninth seasons, a massive cull saw Casualty lose seven main characters, one of whom had been on the show four seasons.) But perhaps one of the most prominent cases was in ITV's military drama Soldier Soldier: Dave Tucker, played by Robson Green, was the only remaining original cast member and practically synonymous with the series. The last scene of the fifth season has him and his wife breaking up. He is never seen or mentioned again. (Neither is his wife.)
Holly Ellenbogen was a main character who is last seen in the twelfth episode receiving a threat from Richie's wife Fern, who is also never seen again. There is no explanation given for her disappearance, leading to the unfortunate possibility that she may have been hurt in some way by Fern.
A later episode, made to calm fan worries that Holly was killed offscreen, features her husband Perry working as an interior decorator for some of the other characters, and referring to his wife as very much alive, and even having a phone conversation with her.
Professor Slater. A recurring love interest for Jeff throughout the first season, she was involved in a competition with Britta for Jeff's affections in the season finale and hasn't been sighted since. Lampshaded in the second season episode "Intro to Political Science": one of the news ticker headlines on Troy and Abed's election coverage reads "Professor Slater still missing".
Not to mention Ian Duncan of the same show. You'd think a character taking off to "get something in his car" would have him back by the end of the episode or the beginning of the next, but nope.
This is actually Lampshaded in the fourth season. During the balloon episode, Troy asks if anyone else has noticed that Professor Duncan hasn't been around in a long time.
And now subverted in the long run, as it was announced that Duncan would be returning in season five.
Between season three and season four, Chevy Chase quit, causing a scattered handful of episodes in season four in which he guest starred, but mostly spawned a series of interesting excuses for his absence. His repeated disappearances are near completely ignored by the group after they initially acknowledged that he wasn't there.
Particularily ironic considering that he had been previously written out of the series temporarily in quite a graceful way, which apparently could not be replicated
The Cosby Show: Theo's best friend Walter "Cockroach" Bradley appeared frequently during the first half of the series, was very close to the family, and even started to get some individual development ("An Early Spring"), then abruptly stopped appearing without explanation. The episode after his final appearance is even focused on Theo and Cockroach's gang of friends' locker room antics, which Cockroach would normally have been present for. Word still has it that his actor, Carl Anthony Payne II, refused to cut his hair as per Bill Cosby's wishes (the kids all changed hairstyles regularly throughout the series) and was eventually fired or left the show as a result. Sad stuff. And the haircut in question, that was apparently worth leaving the cast of what was currently the most beloved and popular show on television? Snip.
Crossroads: A weird and infamous example is the handyman Benny in this 1970s ITV soap opera. He climbed up a ladder to fix the lights on a Christmas tree, and was never seen again.
From the first season up to the eighth season, the original show had a ballistics expert named Bobby Dawson. However, he disappeared about halfway through the eighth season with no explanation.
CSI: Crime Scene Investigation has Catherine's sister appearing at the very beginning of the pilot... only to never be mentioned or appear again. Later episodes that concern her family history imply that Catherine is an only child.
Season 8 brought us CSI Veronica "Ronnie" Lake for a few episodes leading up to Sara's departure. After "Goodbye and Good Luck", Ronnie is never seen again, without any explanation or mention of her since.
Former CSI and detective Sofia Curtis stuck with the crew for nearly 3 seasons, even making it into the opening credits briefly. However, after the season 8 premiere, she completely vanishes without a word. She does return briefly late in season 11, however, having been promoted to Deputy Chief of the LVPD.
CSI NY: Had this happen with two characters: Det. Kaile Maka (who appeared in season 1 and 2) and coroner Evan Zao (who appeared in season 2).
Curb Your Enthusiasm: The pilot episode had the main character as a father. The kids were never mentioned again.
Had Miss King, a sexy female clerk at Mainwaring's bank whom the writers admit was introduced solely for the purpose of being Ms. Fanservice. She disappears after series two and is never heard from again, although she did play a very small role in The Movie.
A couple of platoon members also disappeared with no explanation: Private Bracewell, who appears in the first episode only (Word Of God states he was cut because the writers felt his character was too much like Godfrey's) and Private Desmond, an Ascended Extra who goes on a mission with the main cast in the episode "Sons of the Sea", then is never heard from again.
Private Cheeseman appeared for one series and then disappeared entirely, with no explanation. Word Of God states this was a case of Shoo Out the New Guy since neither the audience nor the rest of the cast liked him. Cheeseman's storyline was that he was a reporter who temporarily joined the platoon in order to write news stories on them, thus, it can be assumed he left at the end of his assignment; but there is no mention of this in the show, he doesn't get a goodbye and is never referenced again.
Bizarrely, recurring character Dusty Farlow suffered this fate by accident: He appeared in a few episodes at the end of the 7th Season, then left town a few episodes into the 8th. Unfortunately the 8th Season was also the infamous Dream Season and the producers apparently forgot about Dusty (despite his father being a main character), so that per canon he simply vanishes without explanation.
If a house counts, Dallas also did this with Southfork itself. In the pilot miniseries, Southfork is a huge mansion with two smaller houses attached by a breezeway. It is discussed in great detail in the first episode that J.R. and Sue Ellen live in their own little house, and the other house was built for Gary and Valene, and that that is where Bobby and Pam will live. After the first season, they switched to a different real life ranch for the exterior sets, and suddenly the Ewings were all living under one roof in a much smaller house.
Days of Our Lives: Don Craig went to the mail to post a letter and hasn't been seen since.
Kendra was a recurring character in many second and third season episodes but vanished without a trace in the fourth season. This was particularly strange because her brother and (ex-)boyfriend were still on the show. One wonders why she wasn't there to react when her brother got expelled and re-admitted, found religion and abandoned it, got married, etc.
Some sources have it that Kendra was planned to have sex with Toby; the actress' parents disapproved and yanked her off the show.
Chris Sharpe, Emma's love interest in season 3; Derek Haig, a notable character until season 9 when he mysteriously disappears; Terri Mcgregor, whose sendoff is only explained in a deleted scene; and Principal Shepherd, former Lakehurst principal becomes acting principal of Degrassi after the merger, is fired due to an outburst at Claire, returns briefly after attending anger management classes, but is suddenly written off and replaced without explanation by old Degrassi principal Ms. Hatzilakos.
Ms. H herself vanishes without a word the following season, with Mr. Simpson, the Media Immersion teacher, being bumped up to the top spot.
Mrs. Kwan, who became one of the most prominent recurring characters, played this trope very well. She was the English teacher and a Recurring Character who appeared in several episodes from Seasons 1 to 9, but hasn't been seen in any of the episodes in Season 10. During that exact same season, Mrs. Dawes, the former art teacher, is now taking her place as the new English teacher with no word of Mrs. Kwan's disappearance. It's unknown whether she's no longer teaching at Degrassi or if she's simply teaching English class periods that the main characters aren't in.
This happens in Season 12 to Wesley. His actor revealed the writers ran out of ideas for the character.
This was also common in the original series too. For instance, a character named Susie Rivera was sexually assaulted before she disappeared. Another character named Scooter Williams did the same thing. Another example is Melanie Brodie.
In Season 3, Martha meets Tom Milligan, and in Season 4 reveals that she's engaged to him. However, by the end of Season 4, it turns out she is married to Mickey instead, and no explaination of what happened to Tom is ever given.
In the classic series, Khameleon boards the TARDIS and promptly vanishes for a long time, because the one crewmember actually capable of operating the robot died. Khameleon eventually returned (by way of an actor covered in silver paint) and destroyed.
Drake & Josh: Drake's original band members, Scottie, Rina and Paul are never seen after the 1st season.
The first season had Drew's Wacky Neighbors, who vanished when it became more of a workplace sitcom and focused on Drew's Wacky Friends. Occasionally, Drew got new neighbors—sometimes being written out, sometimes getting Chucked.
Bob the receptionist, to the extent that some people now call this trope "being Bobbed". The thing about "being Bobbed" is the character has to have just become interesting when they vanished. In Bob's case the County staff had recently discovered the "simple" foreign janitor rather patronizingly nicknamed "Bob" because Doug couldn't be bothered to learn to pronounce her real name was actually a vascular surgeon in her native Poland. Also Maggie Doyle, who would disappear for long periods of time before reappearing, to the extent that this trend was called "being Doyled". Ironically, Doyle herself was eventually "Bobbed".
Speaking of Doug, on two separate occasions in Season 1, he mentions having a son. Aside from the fact that the boy is 8 and that he's never met him, the audience is told nothing else. This is never mentioned again, not even during storylines where it would make sense—his abusive Disappeared Dad resurfacing, his and Carol's efforts to have a baby, etc. At one point in a later season, when asked if he has any children, he says "no".
Ellen: Ellen's friend Anita was abruptly dropped after the first seven episodes were produced, while Holly was never seen or mentioned again beginning with season 2. Paige Clark was introduced at the start of season 2 as if she'd always been there, and an establishing shot of her apartment was the same building used for Anita's apartment in season 1!
Whatever happened to Spenser, Henry's assistant? (Possibly he was fired for hijacking an experimental satellite to watch pirated movies, and for nearly causing impromptu surgery on a visiting political figure, but it's never mentioned.)
But Spencer wasn't part of the group that was with the politician, he was at Beverly's when it happened.
Ditto Greg Germann's character from the pilot, who suddenly vanishes in the second episode and remains forgotten, even though his obnoxious assistant, Fargo, remains.
He is implied to have been fired (or Reassigned to Antarctica) for letting a dangerous experimental device (namely, the Tachyon Accelerator) be taken outside of Section 5 and nearly causing the end of the world.
Callie Curie, an apparent love interest for Carter toward the end of Season 2, doesn't come back, is never mentioned and never addressed as to what may have happened to her.
Let's face it, half the scientists of the week. Which is probably for the better, surely at some point someone would have just realized ten minutes into an episode that some guy from two season's back could probably just save the day.
Family Matters: Judy Winslow, the youngest daughter, simply vanished after the fourth season. Several minor characters also disappeared with no on-screen explanation: Laura's best friend Penny, Eddie's sleazy best friend Rodney, and Carl's boss Murtaugh.
Fire by Nite: This youth TV series had a serial sitcom embedded, entitled Family First. The family originally had two boys and a girl. When the actor who played the younger son moved, and the parents were replaced by a different couple, the younger son, Robert, disappears. They refer to him as if he's off camera for a couple of episodes, but eventually, through the 3-year run of the show after that, he is never mentioned again.
The Fresh Prince of Bel-Air: Jackie appears at one point as a friend of Will's from back in Philadelphia. Throughout the season, she is built up as a potential love interest for Will, until an episode where Will gets into a drinking game with her date, during which Jackie disgustedly asks Carlton to drive her home. The rest of the episode is about Will's dream, delivering An Aesop about drunk driving and Jackie is never mentioned again in the show's run.
A more egregious example is Will's relationship with Lisa Wilkes, he dated her throughout season five and she was the most important relationship he ever had. They became engaged but on the day of their wedding they decided they weren't ready to get married and called off the wedding. Lisa was never seen or even mentioned in season six.
Friday Night Lights: Santiago just seems to have disappeared from existence between season 2 and 3. Ditto Waverly from season 1.
Friends: Phoebe's biological mother, played by Teri Garr. Discovering and reconciling with her down had been a major point of development in Phoebe's life, but after a few appearances, she never came up again.
The exact same thing happened with her biological father Frank Buffay after his one-shot appearance. Phoebe spent literally years trying to track down over the course of multiple seasons. Whole subplots of certain episodes basically revolved around it. Then they finally meet, and after an emotional(if awkward) reunion, he never appears again.
After Emma was born, Ross seems to forget he has a son and Ben is last seen in Season Eight, and even then with Phoebe rather than Ross. Carol is last seen in Season Seven, and Susan disappears in Season Six. Ben's disappearance was lampshaded in 'The One Where No One Proposes': Ross' father, Jack, is looking at Emma and says "look at her, my first grandchild", when Ross asks about Ben, he says "Well of course Ben, I meant my first granddaughter!" then turn to Monica making a "I totally forgot about him!" face. The fact that they never show or address Ben meeting his new sister is pretty egregious.
Fringe: Agent Amy Jessup appeared in the first two episodes of season two, and hasn’t been seen or mentioned since. This could be attributed to fan anxiety that Jessup would replace Olivia Dunham, who started the season comatose.
Despite being one of Robb Stark's key supporters (and the first to declare him King in the North in the season one finale), Greatjon Umber is conspicuously absent from seasons two and three due to the actor portraying him being unable to appear due to scheduling conflicts.
Alliser Thorne was sent by the Night's Watch to King's Landing with a dismembered zombie hand and a request for reinforcements at the end of season one. He hasn't been seen since. Though the actor is slated to return in season four, which may clear the situation up.
This fate befell many characters including their dog Mr. Needles, Accident Amy, Randy, and George's long lost sister Linda.
Linda most likely stayed away from George due to the revelations of how she was put up for adoption and how her birth family is, mixed with George's father-in-law's failed attempt at romancing her.
Randy, Benny's love interest played by Nick Offerman, first appeared in the first episode of season 3, and continued to appear regularly until he broke off his marriage with Benny. Randy only appears once more after this, in season 4, and is never seen again.
Possibly a Justified Trope with Amy, since she was played by Sandra Bullock, who possibly wouldn't have had time to appear consistently. Amy only appears periodically anyway.
The Golden Girls: If you happened to see the pilot episode, you may recall that the roommates had a live-in cook, a flamboyantly gay man named Coco. The character of Sophia, who was only supposed to have appeared periodically throughout the series, turned out to be so popular with test audiences that she was moved into the house to be a permanent part of the cast, and Coco got puffed.
Good Times: Esther Rolle left (temporarily) the series at the end of the 1976-1977 season, with her final storyline being her character Florida's wedding to Carl Dixon, an avowed atheist, and the new couple moving to Arizona (to allow Carl to tend to his failing health). Rolle — already upset about the perceived over-emphasis on Jimmie Walker's J.J. character, strongly objected to the storyline, contending that Florida was an affirmed Christian was now being expected to live with someone with whom her religious beliefs would conflict. When Rolle agreed to return to the show in 1978, one of her demands was that there would be no mention of Carl or her ever marrying or even meeting him, period. The writers agreed.
Aaron, Serena's boyfriend and Cyrus's son. Aaron and Serena were heading off on holiday to Argentina, but you find out the next episode that they broke up on the flight so that Serena and Dan could get back together.
Pretty glaring, considering that he's Blair's stepbrother and appears to be close with his father, yet he never shows up for family events.
The Greatest American Hero: Ralph's son Kevin disappears after the first season. He is mentioned in the the second season episode "Operation: Spoilsport", but not seen.
Grounded For Life: The dog was tied to a fence in the first episode and then seemed to vanish.
H2O: Just Add Water: A few characters from season 1 disappeared with no explanation in season 2, such as Miriam and Emma's love interest Byron.
Mikayla's (Selena Gomez) last full appearance has her becoming friends with Miley despite her hatred of Miley's alter ego Hannah Montana which she was unaware of. This could have easily been played with after Miley outs herself as Hannah Montana. Mikayla is last referred to on a TV show using (likely) archive footage from her earlier 2 appearances and is never mentioned again. Behind the scenes, Selena Gomez had been cast as Alex in Wizards of Waverly Place.
Also lampshaded in commercials run by Nick at Nite after they started airing Happy Days. The commercials featured the narrator talking about Chuck's disappearance and treating it as a great mystery/conspiracy, showing a clip of Chuck's last appearance followed by a clip from a much later episode of Howard saying, "I have a lovely daughter and a loudmouth son."
A new commercial bump on the Hub warns it's viewers and 'forgotten loved ones' of the dangers of coming down with Chuck Cunningham Syndrome, stating the only cure is to find Chuck Cunningham himself.
The Hardy Boys Nancy Drew Mysteries: The Hardy Boys' best friend Chet Morton & their gal friday Callie never appear again after the first season. Nothing's mentioned, nothing's said....
No one's seen, heard of or even mentioned Monica since the season 2 finale. Doesn't look like anyone's missing her either. Although What she did during season 3 is being revealed in some graphic novels following Micah.
Let's not forget Hana Gitelman - though the graphic novels are doing their best to explain what happened to her.
Zach, Claire's friend in Season 1, also caught this syndrome. Admittedly, Claire permanently left his town 4 episodes after his last appearance, and his actor had other commitments, but it's still a little jarring how he's never even mentioned again.
There's also Caitlin, who is never mentioned again past season 2.
Anyone remember Lyle, Claire's brother? Don't worry, neither do her parents. When Claire's in college, her mother, mother's boyfriend, and HRG, and HRG's sort of mistress, all have a Thanksgiving with Claire, but there's no Lyle in sight. Lampshaded later on in this exchange where Sylar remembers the name of Claire's dog over Lyle:
Sylar: "Everybody dies. Well, almost everybody. Papa Petrelli, Mama Bennet, Mr. Muggles. What's your brother's name, Larry?"
Sylar: "Lyle, right. He's gonna die too."
Hogan's Heroes: In the last season, Sgt. Kinchloe abruptly disappears. His role as radio man is taken over by Sgt. Baker (who previously had been one of many prisoners who basically loitered around in the background during scenes to show that there were more than five people in the whole camp) and no one even mentions him again.
Home Improvement: During the first season, Jill has a friend named Maria who shows up quite a bit, the next season, Maria has vanished and is never mentioned again.
Jason Winkler is the most notorious example, as he was given good development, had some romantic subtext with one of the main characters, and was pretty handsome- but after season 1 he was never mentioned again. The fans haven't forgotten him, however, and constantly wait for his return.
Mick Campbell, too. He was a main character in season 1 then got demoted in season 2, but was still pretty important. Come season 3 he was never mentioned, though his actor DID get a cameo in the finale, delighting fans enormously.
Other characters who have gotten this treatment, but AREN'T as missed by the fans, are Vera Devinish, Amelia Pinches, The character's family members, among others. It is in fact very rare for a character who isn't a secondary character to make a return or get a mention in this show.
How I Met Your Mother: Ted's sister Heather visits because she is interested in moving to NYC. The ending scene of the episode is Ted presenting her with a briefcase and a lease for her new apartment that he co-signed. And, yet, she is never seen again, even at her own mother's wedding! We also see Barney's half-sister Carly once and Robin's sister Katie once and never hear about them again.
Many minor characters from the first season have never come back again like the mean popular girl from Nevel's intro episode and "Germy" Jeremy. Though since in-show he was sick all the time there might be another reason why.
Not just first season characters either. Wendy, a popular minor Ensemble Dark Horse character simply vanished as well after her last appearance in the final episode of Season 2.
Tasha, Gibby's recurring girlfriend from a handful of episodes in Season 3, appears to have suffered this fate along with a breakup, only in the 8th episode did a reference to her come, and it was that Gibby and her were no longer 'exclusive' in his words.
Brad, who was implied to have transferred to Ridgeway school with Carly, Sam and Freddie wasn't referenced in the first episode of the second half of season 4, despite it taking place in-universe only three days after iOMG which was the last episode of the 1st half. He doesn't show up in the second episode either, despite them doing a webshow in their usual time and place, which he was explicitly recruited to help with. In the third episode, Carly has to cancel a webshow broadcast specifically because Freddie and Sam aren't there. This is the exact thing Brad would be useful for, and specifically what he was hired for. So he's gone.
Basically, if your name is not Carly, Sam, Freddie, Spencer, Mrs. Benson or Gibby, you will not be coming back, especially if you aren't a villain. Only a handful of characters have even made second appearances, and three of them are Nevel, Nora and Chuck, who are all villains. The only other prominent one to come back was Griffin, who showed up in a second episode, Justified because he lives in the same building, and vanished again.
Nina's very boring (but oh so funny and entertaining) uncle Knit Knots: a beloved character who owned a business next door to the Imagination Movers' "Idea Warehouse" that created boring items and services for “boring” people. He appeared in every episode in the first season of the show, but completely disappeared, with no explanation for seasons 2 and 3.
He did make one other appearance in the Imagination Movers' concert special, which aired on Disney during season 3, however, this was a live event, which was not intended to be canon with the series.
The Invisible Man was forced by the network in Season Two to add a new, attractive-to-males character played by Brandy Ledford. The fans didn't like her very much, and there were numerous complaints about how she ruined the Fawkes and Hobbes dynamic. So when the show's cancellation was announced, the writers took advantage of the fact that they had nothing to lose anyway, and just left the character out of the last few episodes with no explanation.
Jesse: In the first season of this NBC sitcom, the title character and her son are seen living with her two brothers, while she works at her father's bar. However, for the second season, the network retooled the series. While Jesse is shown getting a new job, her father and brothers are treated as if they had never been there.
Kids Incorporated: References missing characters from previous seasons through season 5 — Mickey moves away after season 1, Gloria goes to music school after season 3, Renee and The Kid become exchange students after season 4. Even the characters dropped after the original pilot episode are said to have moved away in a scene added at the end of the VHS release. On top of that, each new character is introduced and has to audition for the band. However, when season 6 begins, Ryan and Connie have been replaced by Robin and no one mentions their absence or where Robin came from, then Stacy, Richie, and Devyn are replaced by Eric, Ana, and Haylie for season 7. At this point, more than half the cast is new this season, and only one of them has been on the show for more than a season. And yet we have not a word about this (they do mention, several episodes later, that Ana had only recently moved in with Robin's family after her parents' divorce). As Stacy was the last of the original cast, that her departure doesn't even get a mention is a little grating especially considering who she'dgrow up to become — the departure of Mario Lopez got more notice, and he didn't even have a speaking part. Strangely, Riley, a secondary character, also leaves in season 6, and his departure is a plot point.
Sara Spooner, the younger sister of Carrie, only appeared in about five episodes of season one and disappeared from the show without an explanation. It was later revealed in an interview with show star Kevin James that the writers had no idea how to develop her character so they just decided to write her out.
Doug's sister Stephanie and his friend Richie, both of them vanished without a trace. Doug and Carrie also had two dogs in the first few episodes which disappeared without an explanation.
Doug and Carrie also adopt Stanley, a dog that belonged to one of their neighbors towards the end of season 1. He was shown in the background for the rest of the season, but suddenly disappears for several seasons without any mention, only to suddenly reappear in an episode which featured him prominently in the fourth season, where he was again a background character....only to vanish once again without mention.
Kyle XY: More often than not, this became an Averted Trope in favour of putting people on a bus or killing them off-screen. In the second season, however, there is a glaring example of this trope. After the Madacorp plot is defeated, Julian Ballantine is demoted and replaced by The Dragon, Emily Hollander. The scene in which this happens has suitably ominous overtones, suggesting that the viewer hasn't seen the last of Madacorp. And then Hollander appears in one further episode, attending her company's stand at Kyle's school, and is never seen again.
Eli Duckett, a popular recurring character for 15 years, was never mentioned again after the actor playing him, Danny O'Dea, died.
Ros was never mentioned again after her actress left following the 26th series.
When Tom first arrives in town, he is accompanied by Mrs. Avery, a potential love interest and foil for Nora Batty, and her niece, Babs. Both characters were unpopular, and Babs disappeared after only three episodes, while Mrs. Avery was around for a series. Neither character has been mentioned since their departure despite their former relationship with Tom.
Earlier on, the librarians, Mr. Wainwright and Mrs Partridge, were regulars during the first series but disappeared completely during the second series without mention or explanation. Mr. Wainwright would return for a few episodes during the third season but disappeared completely following the third series and was never mentioned again.
Las Vegas: Sarasvati had been built up in Season 3 as a potential love interest for Mike. The last we see of her is the final episode of the season at Delinda's bachelorette party, where she asks Mike to come to her room. Mike never makes it, and the next we hear Sarasvati had gone home with all of the male strippers. She appears for about five seconds in one episode of Season 4, but other than that is never heard or seen from again.
Laverne and Shirley: Edna De Fazio, the girls' landlady and later Laverne's stepmom vanished sometime after the characters all moved to California.
Paul Robinette. A deleted scene has Stone telling Van Buren that Robinette quit and joined a private firm, but this scene wasn't aired. Robinette resurfaces for a few guest appearances, though.
Nina Cassidy. Considering her performance/Van Buren's reaction to her through the entire season, including her final episode, it's heavily implied she was transferred if not fired. Unlike the others, though, she never shows up again after her disappearance.
Alfred Wentworth, the DA in the pilot, "Everybody's Favorite Bagman," which was the sixth episode aired.
Interim D.A. Nora Lewin after the end of season 12, although this is a slightly complicated one: she left right when there would presumably have been an election for DA, meaning that either she did not run or was defeated by Arthur Branch.
Two of Elliot's daughters haven't been seen since season eight, with a picture reference in season ten. All the more jarring because one of them has a twin brother who had a Day in the Limelight episode.
In the episode 'Totems', Elliot said he has five kids, so they still exist. The other two apparently have normal, uneventful lives.
Lie to Me: Torres' boyfriend served his part in her character development, then faded from the cast's collective memory.
Life With Bonnie: Samantha Molloy, flat-out vanished between Season 1 and Season 2. Especially disconcerting since she was the main character's 12-year-old daughter in a show that had many, many "family at home" scenes.
Life With Derek: Where Noel only had three appearances that were rather influential (i.e. he was partially the reason why Casey broke up with Max in the episode "Allergy Season"). It was even set up in the episode "Just Friends" where Casey and Noel would become a couple... except not, apparently.
Cat Grant disappears without a trace after the first season, ostensibly because the network thought she was too risque. Increasingly important character Jack, who'd been the focus of some serious character development over the course of the season, showing Clark's positive influence on people, disappeared with Cat. Disappointing to say the least.
Lucy Lane felt like this - a regular in the first three episodes, then vanished without a trace. She would make a few more appearances, though, by a different actress and with a very different relationship with Lois, as if they'd forgotten about Lucy's earlier days.
The Loop: This Fox comedy is a particularly bad example of this. Between the first and second season, both female leads simply disappeared without a trace. The reason this is so unnerving is one of the female leads was the main character's love interest, and their relationship was left completely unresolved.
The character Isabel is introduced as "the sheriff" of The Others in a season 3 episode. She investigates Juliet after Danny's death, and seems to be a high-ranking member of The Others' hierarchy. She is never seen or mentioned again, and producer Damon Lindelof said that she was killed offscreen when the Others attacked the beach in the Season 3 finale.
In a bizarrely large-scale example of the trope, the Others themselves disappear completely after the season 6 episode "The Last Recruit" and are never seen or heard from again. They are last seen getting pulverized by mortars, making it unclear if any of them survived. The arguably canon Lost Encyclopedia claims at least three Others—kidnapped flight attendant Cindy and children Zach and Emma—survived the bombing, but the fates of the rest of the Others are never known.
Mad About You had Paul's friend Selby vanish, last seen at the end of season 1 (Lampshade hung in one episode when Paul, complaining about their lack of friends, yelled, "Like Selby, what the hell happened to him?").
Cynthia, a recurring character, originally has a one-sided crush towards Malcolm. She goes to Europe and when she comes back, is all grown up. Malcolm eventually re-considers her as a potential love interest. In her final episode, she loudly proclaims in front of the whole school that they had previously been intimate. And then, without explanation, she never appears again.
Some of the Krelboynes that appear early in series aren't seen again later, though a few of Malcolm's closer circle (Stevie, Dabney, etc.) remain.
Married... with Children: Seven, a Cousin Oliver introduced in Season 7, was written out without explanation when he proved unpopular with the fans. Lampshaded in one episode when his face was seen on a milk carton and no one in the Bundy family noticed or cared. Another episode, "Kelly Knows Something", showed that Kelly could learn things, but for every new fact she learned, another fact would be forgotten. While cramming for a quiz show, a visual gag shows new facts going into her head as old ones exit... including the existence of Seven, apparently.
Rhoda has a sister Debbie who is not seen at all when Rhoda got her own series. Debbie appears on an episode where Rhoda and Mary go to New York for Debbie's wedding. Furthermore, Rhoda's sister Brenda is nowhere to be seen.
Rhoda also mentions once, on The MTM Show, that she has a brother, and therefore does not need to have the purpose of a bar mitzvah explained to her. It's one line, but her brother is never mentioned again. This could be explained as Rhoda lying, just so a person who tends to ramble on, doesn't go on and on explaining bar mitzvahs, but it doesn't sound that way.
Likewise, The MTM Show has possibly TV's first blatant, non-judgmental, declaration of a character as "gay," using that exact word; it's a punch-line that is built through an entire episode, in that Phyllis is horrified that her wonderful brother is spending time with Rhoda, whom she can't stand, and not with Mary, in spite of Phyllis's efforts to set up Mary with her brother. At the the end Rhoda tells Phyllis she isn't interested in her brother because "He's gay," and Phyllis says "Thank God!" When Chloris Leachman gets her spin-off, Phyllis, the brother is never mentioned.
What ever happened to Spearchucker Jones or Ugly John?
The Real Life explanation is that Spearchucker was dropped when the writers were informed that there was no record of any African-American doctors serving in the Korean War. (There is now a Web memoir that mentions an African-American surgeon at a MASH unit.) Ugly John has no explanation, real life or in-universe. (Though curiously enough, the actor who played him later showed up playing a different character in the season 8 episode "Captains Outrageous"
Matlock: Ben has a daughter, Charlene, played by Linda Purl, during the first season, who leaves to marry some prosecutor. He occasionally refers to "my daughter." Later in the series, Brynn Thayer comes on as his daughter, LeAnn, who just divorced a prosecutor she was married to whom Ben didn't approve of.
Merlin: Had Geoffrey of Monmouth, the court geneologist and librarian who was often used for exposition purposes. A Recurring Character throughout the first four seasons, he was completely absent from season five without explanation.
Mission: Impossible: All cast changes on Mission Impossible occurred without explanation, except for the switch from Terry Markwell's Casey Randall to Jane Badler's Shannon Reed in the revival, when poor Casey is caught and killed. (Needless to say, the Secretary disavows all knowledge of her actions.) But only Dan Briggs, the original IMF leader, is a genuine Chuck Cunningham (replaced by Jim Phelps because Steven Hill refused to work on the Jewish sabbath). Other changes are explained by the way the leader chooses the rest of the team after he gets the assignment. The fact that he chooses the same people over and over is actually a kind of reverse Chuck Cunningham. <— Is there a trope name that describes this better than "reverse Chuck Cuningham"? —>
One of the early television masters of this art. It happened more than once, and in a deliberate fashion. First, William Frawley, veteran comedic actor (I Love Lucy's Fred Mertz) played Fred MacMurray's father-in-law, Bub O'Casey, the boys' grandfather and housekeeper. When Frawley (very begrudgingly) left the show when his poor health meant he could no longer be insured, that was when William Demarest's Uncle Charlie was brought on, with Bub sent home to Ireland. Eventually, any and all references to Bub simply vanished. When the show moved from ABC to CBS and started color episodes, eldest son Mike married his sweetheart and moved away. Orphaned neighbor Ernie was adopted after some wackiness - and again eventually both Mike and the fact of the adoption vanished from mention. Steve's new wife and her daughter joined late in the show's run - but the signs were already there and references to a pre-Douglas life dried up for the two. So: Uncle Charlie was *always* their housemaid/gruff mentor, Ernie was *always* the third of three sons and no more, and the new Mrs. Douglas and child had *always* been there as well. This is the word of Fred MacMurray.
Not quite. Once, post-Ernie, Steve shows someone Mike's diploma, framed on the wall, along with Robbie's. Another time, when Steve is about to remarry, Robbie tells his wife that he doesn't remember his mother very well, and he doesn't think Chip remembers her at all. He doesn't mention Ernie, in a nod to the fact that she isn't Ernie's mother, because Ernie was adopted by Steve after Robbie and Chip's mother had already died.
There was, in fact, a single line, when Steve was adopting his new wife's daughter. Ernie says at the breakfast table, "You know, I was adopted, too," and it drops right there.
Mike's vanishing was slower than all that - on one ep, when it seemed Steve might end up in a circumstance where he couldn't have them around, the younger boys discussed possibly living with Mike. As to Ernie in that later sequence, it could be a nod to his adoption, or it could be a way of saying, 'If the older Chip doesn't recall their mother, then Ernie has no chance at all'. No one ever states that Bub/Mike/the adoption never happened. They just avoid all instances in which it might be brought up, to the point where certain Bub flashbacks now have Uncle Charlie edited in.
Mystery Science Theater 3000: The actor who played Dr. Erhardt left the show after the first broadcast season over creative differences. His disappearance was simply explained with his replacement, TV's Frank, holding up a milk carton and stating "He's missing." His disappearance was the butt of a joke in Earth vs. The Spider, when a policeman who looked similar to the missing Erhardt was eaten by the titular spider. Joel and the Bots joked that this was the true fate of their former captor.
Naturally Sadie: Tad, a friend of Ron Yuma and Rain is a recurring character during season 1; he's never seen or heard from after the Re Tool.
During the first two seasons, this happened several times - starting with the second episode. The original public defender, Sheila, vanished from the show and even failed to make the listing for the show on IMDB!
Also happened to a popular pair of recurring characters, Bob and June Wheeler, a married couple of hard luck hicks. What made their disappearance feel especially abrupt is that in their last episode, it was implied they were about to have a semi-regular presence on the show, since they just bought and began running the Court cafeteria. And to make their departure all the more jarring, their last episode was a Season Finale that ended on a Cliff Hanger. In the next season premiere, the Cliffhanger is resolved, but with no sign or mention of the Wheelers. The Real Life reason for their disappearance is that the actor who played Bob, Brent Spiner, was cast as Data on Star Trek: The Next Generation in between seasons.
A few extras from the pilot of disappeared after the cast began to fill out the workplace....
Erin's foster brother is introduced in one episode, and promptly drops from the face of the Earth afterwards.
Jevon from Only Fools And Horses, who was Mickey Pearce's trading partner in the sixth season, vanished without a trace after "The Jolly Boys' Outing". Unlike most of the other semi-regular characters that left the series, he was never mentioned again after his disappearance.
Once Upon a Time: The first season featured the recurring character of Sydney, who in Storybrooke is the town's newspaper editor and ally of Regina; in the Enchanted Forest, he is the Magic Mirror and Regina's confidante. In Season 2, the character is completely absent, after last being seen incarcerated in the local hospital. Despite there being no reason for him to be imprisoned, he is never seen in the post-curse Storybrooke, nor is the Magic Mirror seen anymore in flashbacks — until Season 3, when the back of the mirror is shown and his voice is heard. In real life this is due to the actor being cast in a major role in another series on another network, Revolution, thus becoming unavailable for even guest appearances. But Sydney's absence - especially during the flashbacks - is noticeable.
The Paper Chase: In the first episode, the study group included a woman (Asheley) who never appeared again - although for some reason Deka Beaudine, who played her, was not only listed in the opening credits of every season one episode but also received an "And" billing. In the second episode, she was replaced without explanation by a different woman, Logan, a major character throughout Season One. When, after cancellation on its original network, the series returned for Season Two on a cable network, Logan had inexplicably vanished, never to be mentioned again.
Desiree (Mari Marrow), Nikki's best friend, simply vanished about halfway through the first season and is never mentioned again. A few episodes later, she is replaced by Andell, a character from parent series Moesha. This is especially jarring considering that Desiree lives next door to the Parkers. Her disappearance from the show can later be justified as Nikki eventually moved into Kim's apartment...but that still didn't happen until a season after she disappeared.
Scorpina double subverts this trope, disappearing the moment Lord Zedd shows up, only to appear in one episode fighting the Rangers, surviving and never being seen or heard from again. Behind the scenes, she had been scripted to return, but Saban could not get the American actress back and the plot line was dropped instead.
Angela, Zack's love interest, disappeared after the first season. Richie, Trini's love interest, and Curtis, Zack's cousin, both disappeared after Trini and Zack were written off the show.
During the transition between Power Rangers Turbo and Power Rangers in Space, Lt. Jerome Stone, as well as the Angel Grove Youth Center and Juice Bar, disappeared and was replaced with Adelle and the Surf Spot.
It was previously averted with the previous Juice Bar owner Ernie whose absence was explained as a trip to the Amazon.
Sometimes, Bulk and Skull would occasionally be seen with various nameless thugs, as part of what we are led to presume is their 'gang'. They only appeared for certain early season 1 episodes, and then seemed to disappear forever.
When Jason returned in Zeo, he met Emily who became his love interest. He departed at the end of Zeo, going off with Emily, and appearing again in the Turbo movie but without her. He then disappears until the tenth anniversary special.
That's not even the true mystery. It's Emily that's the mystery. She has one more on-screen and named appearance in Turbo, which lasts for a few seconds and without Jason, then she's never seen again at all.
Squatt and Baboo, where are they in Zeo? They used to cling onto Rita, and yet when she, Zedd, Finster, Rito and Goldar are forced out of their home, and made to travel around in their caravan, it seems Squatt and Baboo just kinda...vanished. Unless they were destroyed by the Machine Empire off screen.
They went to stay with Master Vile to regroup; maybe they stayed with him when the others went back to the moon.
Reaper: Sam's brother appears in the first two episodes and then is never seen or mentioned again for the rest of the show's two-year run.
The second season introduced a host of new characters, none of whom were ever seen again afterwards, save for the odd reference here and there.
There were also Glen Brachston, the lazy marina owner; Garth Harble, the first animal control officer before Ed Frid; Earl Battersby, the bait shop owner; Dwight Cardiff, the other lazy marina owner; Dougie Franklin's brother, Benjamin; Bob Stuyvesant, golfer/ministry of natural resources worker; Arnie Dogan, accident-prone roofer/aspiring country singer; Young Walter, who substituted for Bill in the later Adventures With Bill segments; Dale, a teenaged boy who worked at a local gas station; Kevin Black, a Yuppie cottager; Brian Jacobs, funeral parlor owner; etc. At least one was justified, as Red mentions in one segment that Garth got bit by a toad and "lost his nerve," and thus was replaced by Ed.
Happened repeatedly over the course with family friends and neighbours. The most egregious example was easily Roseanne and Jackie's best friend Crystal Anderson, whom they'd known since childhood and was an official main character for the first few seasons, appearing in the opening credits and everything (a rank never even granted to the Healy brothers, despite them living with the Conners and appearing prominently in almost every episode in the second half of the series). After she marries Dan's father Ed (a recurring character played by Ned Beatty) and bears two children with him, they all vanish for a season or two before prominently appearing again in a two-episode arc about Dan reconciling with his father. After that, Dan's father did not appear again and Crystal returned for one last appearance at Roseanne's baby shower at the beginning of the 8th season. Neither of them appeared after that, even at extremely notable events such as Darlene's wedding, or in the final season when the Conners won a hundred and eight million dollars in the lottery.
One neighbouring family introduced a few seasons into the series got tons of episodes and development, including one daughter pursuing main character David Healy and her overweight wallflower sister catching Roseanne's attention as somebody who needed support and guidance. The Conners even all traveled to California with them in an RV at one point. Unlike their previous sets of neighbours who'd had proper send-offs, they eventually just stopped appearing.
Jackie's husband/ex-husband Fred stopped appearing altogether a couple episodes after they divorced, although was occasionally referenced as taking care of their infant son in various episodes. Like other characters, his absence in the face of the Conners winning the lottery (including his best friend and boss Dan, his ex-wife Jackie and his infant *son* Andy) is nigh-inexplicable.
There's also the absence of Bonnie, the waitress from Rodbell's with whom Roseanne worked. Somewhast justified in that everyone seemed to have gone their separate ways after the Rodbell's diner closed down - Leon, her boss, vanished for a while before resurfacing after Roseanne and Jackie opened their own diner, and stuck with the show afterward. Bonnie, meanwhile? Just gone.
Anne-Marie and Chuck also vanished. Anne-Marie was a friend of Roseanne's from high school, while Chuck became friends with Dan through their wives and regularly participated in the men's poker games.
Damn near everyone from the plastics factory disappeared after the mass walkout. Vonda stuck around for a little bit into the second season, even having a singing part in the musical episode and setting Roseanne up for a job interview. Then she was replaced by Anne-Marie as the Token Black Friend.
The salon crew got plenty of screentime and development during Roseanne's tenure, and the whole setting felt like a possible test for a spinoff launch. But, after Roseanne getting into an accident with one of the regular customers, she's never shown working at the salon ever again, and no mention is made of why. (Presumably, her job was filled while she recovered.)
Had two characters at the end of season 1 who disappeared without explanation: Sabrina's supposed "best friend" Jenny (who might have been referred to in passing as "Jennifer" in a later episode) and Mr. Poole, the science teacher.
Mr. Poole may have a bit of an excuse, as he wouldn't be Sabrina's teacher due to her moving up in the grades.
It's also never mentioned what happened to Dreama, the girl Sabrina was supposed to be coaching for her Witches' License.
The character of Miles also vanishes quite suddenly.
It happened in the original Saved by the Bell too, but to a lesser extent. The most egregious example was the replacement of Jessie and Kelly with Tori for the last season. That is, until the graduation finale, where the process was reversed. Neither was given any explanation. What really happened was after the series finished production, the network ordered more episodes. The actresses declined to return for them, thus necessitating Tori. The finale was filmed before this happened.
Saved by the Bell is actually one of very few shows where the MAIN CHARACTER got Chucked. In its first season, the show focused on the kids' teacher, Miss Bliss, and the school faculty in general; the kids were meant to be supporting characters. This setup was quickly abandoned once it became obvious that the students had a lot more potential for comedy and stories than the teachers. Miss Bliss vanished from the show between seasons one and two. Even the SCHOOL ITSELF fell victim to this trope — in season one, it's a junior high school in Indiana. From season two on, the same cast is attending a high school in California. No explanation is ever given.
Saved by the Bell is sort of an re-imagining of a different show, Good Morning, Miss Bliss, which was then shown in later syndication as though it were the first season of Saved, despite the resulting oddities in continuity.
Scrubs: Dr. Grace Miller was introduced with much fanfare in season 3, then promptly vanished off the face of the earth. Series creator Bill Lawrence later explained that this was because Miller had been a failed attempt to create a female Dr. Cox character. This didn't work because A) it was redundant, as Jordan more than adequately fulfils that role, and B) Dr. Miller was an unfunny, unlikeable shrew.
Secret Diary of a Call Girl: In one of the earlier episodes Hannah goes to the hospital to visit her sister Jackie who just had a baby boy. Later she goes to her new nephew's christening. But when Jackie separates from her husband and stays for awhile with Hannah, the baby is not only nowhere to be seen - he isn't even mentioned once.
Oddly enough, given the show's notable sensitivity to such subjects, when Northern Calloway (David, then owner of Hooper's Store) left due to illness and died a few months later, no explanation for the character's absence was ever given on-screen then or since. He seems to simply have been deleted from Street memory.
Word Of God has it that it was too soon after the death of Mr. Hooper (in a memorable Tear Jerker, the adults had to tell Big Bird Mr. Hooper had died, some time after his actor Will Lee died) for there to be another death. And apparently they didn't really feel like coming up with some other explanation for David's departure, so his disappearance was never explained and the show just moved on.
Another explanation that has appeared in published accounts was that Calloway had become involved with drugs and was involved in several instances of inappropriate behavior, run-ins with the law, and repeated conflicts with the production staff and cast. These accounts sometime contend that David simply had (off-screen) moved to Florida to care for his grandmother, with no other explanation or reference given; David's grandmother had appeared several times from the late 1970s through mid-1980s.
Additionally, numerous Muppet characters have come and gone for various reasons and are now no longer on the show. One was Don Music, a piano player who bangs his head against the piano in frustration, who was dropped from the show when kids at home started doing the same thing. Another was Harvey Kneeslapper, who was let go because his signature laugh was too much of a strain on Frank Oz's vocal cords. Then there was Roosevelt Franklin, who was arguably one of the first breakthrough Sesame Street Muppets, but who was dropped since he was considered to be a negative cultural stereotype (he was the only African-American Muppet at the time and was seen mostly in detention after school). Finally, Professor Hastings, a teacher whose lectures were so dull that he would put himself to sleep while giving them, was discontinued because he was too dull.
Space: 1999: Had quite a few characters disappear between its first and second season. From the regular cast, Paul Morrow, David Kano and Victor Bergman were suddenly gone without explanation. The Moonbase Alpha Technical Notebook explains that all three died... and apparently lines of dialogue were written to that effect but never used, making their absence all the more glaring as there was nowhere they could have gone (Not quite. Morrow and Kano's absences are never explained, but the Season 2 opener "The Metamorph" confirms in dialogue between Verdeschi and Sandra Benes that Victor Bergman died due to a malfunctioning spacesuit). A recurring character, Tanya Alexander, also went missing. Dr. Robert Mathias, Helena's assistant in the medical center, was briefly used in a much smaller role but then disappeared (again, the tech notebook "explains" that he changed sections). This was compounded when Tony Verdeschi started in like he'd always been there in their place at the beginning of the season.
Spin City: This show was well known for this — of all the characters who left, only Mike (Michael J Fox) actually had an exit storyline. This meant that, over the course of the series, Stacy, James, Nikki, Janelle and Angie all disappeared without trace, often with only the barest of mentions (Catlin: I fired James.).
Dr. Ben Samuels was a major character in the first season who simply stopped appearing. His plot arc was never resolved, and none of the other characters mention him again. This makes sense, considering he only existed in the mind of Tommy Westphall.
Dr. Hugh Beale suffered this fate as well.
Stargate Atlantis: Has Hermiod, a recurring Asgard on the Daedalus introduced in Series 2. He later vanishes without explanation, though Word Of God claims that he died in the Asgard mass-suicide in the SG-1 finale.
Re'tu Charlie is never seen after going to live with the Tok'ra in "Show and Tell", despite his closeness to Jack and despite many further Tok'ra episodes.
Nyan is never seen after being becoming Daniel's research assistant in "New Ground".
Teal'c's love interest, Ishta vanishes after season 8 and is never mentioned again.
And of course, Jonas Quinn, a member of SG-1 for a whole season, completely vanishes after season seven's "Fallout". He isn't mentioned when when his homeworld Langara is said to have been conquered by the Ori, nor does he reappear when they actually show Langara in Stargate Universe.
The Tok'ra Anise was introduced to 'sexy up' SG-1 for ratings, but was removed without any fanfare after a few episodes when the show runners decided the ratings were fine as they were.
The Andorians can be seen as an entire Chuck Cunningham species in this universe - Star Trek: The Original Series set them up as an important member of the Federation... by The Next Generation, they're all gone. The Word Of God explanation was that they were just too silly-looking (blue skin and antennae...).
In "The Offspring", Data's Truly Single Parent daughter, while choosing an appearance, narrows down the list to a few choices, one of which is an Andorian female. It's mentioned that if that appearance, she would be the only Andorian on the Enterprise. And that was the only Andorian appearance in the 24th century shows... they got a few other off-screen mentions, mostly in Deep Space Nine since some they seem to have done trade there. But off-screen.
The Tellarites were also important in TOS, but don't appear in the 24th century—unless you count background appearances from recycled footage.
The fun thing is, Star Trek: Enterprise (a prequel series) set these two up as the third and fourth most important species in the Federation. On one hand, it compensates for their non-appearances. On the other hand, it makes their apparent disappearance all the more puzzling.
The EU explains that the Andorian's apparent disappearance is because they are having a genetic collapse of the Andorian species and aren't even able to maintaining their current population. This is not helped by the fact they have four genders and require all of them to reproduce. Thus, every able-bodied young Andorian is expected to be on Andor attempting to raise a family, not be running around the galaxy in Starfleet. There's still no explanation for the lack of Tellarites, although it's possible they simply aren't well suited to Starfleet.
Also the Orions, the race the originalGreen-Skinned Space Babe belonged to. ( Well, it was an illusion, but anyway...) Like the Andorians and Tellarites, Deep Space Nine had a lot of fun with keeping them a just-offscreen big deal. In fact, an episode had Ezri's family involved with the Orion Syndicate. All dealings with them are through their non-Orion enforcers. Also like the Andorians and Tellarites, Enterprise brought them back in full.
Both the Andorians and the Orions also play very large roles in the MMO, Star Trek Online.
In the Original Series, Yeoman Rand was set up in the first dozen or so episodes as a regular love interest for Kirk and then disappeared without explanation. No one seems to be quite sure of the reason (several seemingly contradictory explanations have been given by people involved in the show), but it's usually claimed either that the writers decided Kirk shouldn't be held down by a steady girlfriend and should have Girls of The Week instead. She did, however, return in the films, ending up as Sulu's first officer on the Excelsior.
An odd case from Star Trek: Voyager: Samantha Wildman, whose daughter Naomi remained on the show with Seven of Nine basically taking over the mother role for her. Word Of God is that the writers somehow got the idea that they'd killed Samantha in an episode where she almost dies but pulls through.
Another similar case on Star Trek: Voyager was Lt. Joe Carey, an assistant engineer who appears in four first season episodes... and then not again till the fifth season, and in a flashback at that! One wonders if here again the writers thought they killed him off at some point, since his presence is used to indicate an earlier time. He then reappears exactly twice in the remainder of the series, and gets killed in the fifth to last episode of the series. A run of bad luck.
When Gates McFadden reprised the role of Dr. Crusher in the third season of The Next Generation, her second-season replacement, Dr. Pulaski, simply vanished with no explanation given.
Deep Space Nine: Remember T'Rul, the Romulan who was part of the command staff of the Defiant as a stipulation of the Romulan Empire's agreement to let Starfleet use one of their cloaking devices? No? No surprise. (The rules T'Rul was there to enforce also conveniently disappeared without a comment, other than one episode where they simply remembered one of the rules, then broke it.)
The Suite Life of Zack and Cody: The old maid Muriel appeared a lot in season one...and disappeared in the next two seasons. It was revealed in the series finale that she retired two years earlier...and Zack and Cody brought her back due to fact that Mr. Tipton was planning on firing somebody and who better to fire than someone who's already retired?
The writers managed to do this in the span of a single episode in season 5. It introduced Jesse Turner, a young boy explicitly identified as the Anti-Christ. This resulted from a union between a demon and a human, which somehow imbued him with high-level Reality Warper powers, an ability neither species displayed in any way. Possibly realizing how little sense it made that this would result in the most powerful character depicted in the show up to that point (with the possible exception of God) and the Story Breaker Power it entailed, the writers immediately sent the character off to nowhere, and he's never mentioned afterwards. It's technically also Put on a Bus, but it goes straight past even Long Bus Trip because everyone immediately forgets he ever existed at all.
Taxi: In which John Burns disappears after the first season without on-screen explanation (though he may have been fired for crashing the beloved Cab 804 beyond repair; Word Of God is that he was just too boring a character.)
In the fifth episode, Donna's sister Tina is introduced... only to never be seen again. Later in the series Donna is referred to as being an only child. Tina's disappearance is lampshaded at the end of a season two episode called "Vanstock." A narrator announces a bunch of character questions in a dramatic fashion, such as "Will Donna and Eric ever consummate their relationship?" The final question is "And whatever happened to Midge's other daughter, Tina? Find out next time on That 70s Show!" However, this is the last time Tina is ever mentioned.
Donna's older sister Valerie was mentioned as being at college, and then was never mentioned again. Considering That '70s Show gave many nods to Happy Days, Tina and Valerie may have been intentionally introduced just to have this happen.
The most prominent semi-example is Laurie, Eric's older sister. She was a recurring character in season one, and then a regular in season two and three. Her actress then left the show, and Laurie wasn't mentioned at all.(At least not by name, though Red mentioned having "kids"). Laurie came back (played by a different actress) for recurring appearances in season five and six before disappearing again, though she was mentioned in passing several times. When Kitty considers Donna part of the family at the end of the series, they lampshade on Laurie's disappearance, wondering where she is.
Jeff and Steph Woodcock (Eddie Kaye Thomas and Kat Thomas) were lead characters, on equal footing with Eddie and Joy Stark (Brad Garrett and Joely Fisher), and the whole basis of the show seemed to be about contrasting a newly-wed couple and a long-time married couple. After the first 2 seasons, however, they vanished without a trace, and Jeff's sidekick role was taken by Kenny, played by J.B. Smoove. This was further confused when unaired episodes from Season 2 aired in the middle of Season 3.
Kenny disappeared himself at the beginning of the fourth and final season. His place was taken by their daughter Ally and her fiancé/husband Doug. Like the season before the episodes were aired out of order and had some leftovers thrown in. Since Ally was recast three times during the show it was especially confusing.
This gets a lampshade when Doug remembers all of the above, plus a random guest arc by Gilbert Gottfried, late in the fourth season, due to him getting Medium Awareness as a form of mental illness. Don't worry, it Makes Just as Much Sense in Context. At any rate, none of the other characters have any idea who he's talking about when he brings them up.
This British sci-fi series had Stephen, one of the original cast members, just disappear from the series without explanation after the fourth season. According to some sources, Executive Meddling was the reason for his departure, and writer Roger Price didn't feel like writing the character out... so Stephen is gone from the series without any sort of explanation or acknowledgement that he ever existed. Very jarring, considering he was one of the first people we were introduced to, and was one of the two longest-serving cast members up to that point.
Tyso disappeared at the same time as Stephen (also with no explanation). However, during the fourth season Tyso had been Demoted to Extra due to confusion over whether he'd be returning to the series.
In the remake, Lisa disappeared after the first season and Kevin vanished after the second, with no mention made of either of them by anyone.
Torchwood: Had Detective Kathy Swanson, whom the team reach out to when locked in their Elaborate Underground Base. She disappears after the first series and is never mentioned again, even in episodes that involve the police or take place in the police station (although she does make it into the Tie In Novels.)
The Torkelsons: This short-lived sitcom was completely retooled as Almost Home for its second season, famously losing two of the family's five children in the process.
Trailer Park Boys: Whatever happened to Trina? She and her mom, Barb, were staying with Lahey over the summer, but then Barb was made a recurring character, and Trina drops of the face of the earth.
Tru Calling: This short-lived television show initially had both of Tru's siblings as members of the main cast. While her brother Harrison remained on the show to its final episode, her sister Meredith disappeared midway through season 1 and was never seen or heard from again.
The Tudors: This was actually a rampant problem for the show, resulting in an extensive rewriting of history. Among the important characters who disappear without a trace (and often have their historical roles delegated to someone else) are the Duke of Norfolk, Sir Anthony Knivert, Archbishop Cranmer, Pope Paul III, and Sir Francis Bryan.
Welcome Back, Kotter: Gabe's wife was pregnant, but then it was suddenly forgotten; apparently they were trying to write the actress's pregnancy into the script, and it became a running gag for some time — until the actress had a miscarriage. A year later however, they repeated the same gag, and she had twins.
The West Wing: Mandy was a publicity relations manager for the first season, who disappeared after it. According to Rob Lowe, the writers referred to any character who had disappeared and not been used when they seemed they'd be more important as having 'gone to Mandyville.' Not only did she disappear between season one and two (despite the opener of season two following directly on from the end of the first) but she does not appear in any flashbacks to Bartlett's initial campaign, despite having been established as both working on it and being involved with Josh at the time. Even during Leo's funeral, when a number of old characters showed up, she was neither seen nor mentioned.
They did it again with Agent Garrett Fowler. He was a major villain in Season 1 and the first half of Season 2. He and Neal face off in the mid-season finale, he gives them all the information he has, Peter brings him back to the Bureau, and... nothing. Absolutely nothing. We never find out what happened to him. He gets a passing reference at the beginning of Season 3, but it's only a mention of his and Neal's confrontation. Word Of God doesn't even seem to know. When asked, Jeff Eastin replied, "Peter killed him and buried him in the backyard." Needless to say, this inspired a lot of fan fiction...
Wings: After Thomas Haden Church left, Brian Haley was brought in to play Budd Bronski, the replacement character for Church's Lowell. However, Budd's personality was neither as memorable nor as well-defined as Lowell's had been, so after a few appearances, he disappeared from the series without explanation, and the writers decided to build up the show's other supporting characters (chiefly Antonio and Casey) instead.
We are given the example of Scully's invisible brother, Charlie. He is seen once in a flashback to when they were children, mentioned perhaps twice, and then never again. And though we see Scully's other siblings: older sister Melissa and older brother Bill who have a moderate impact on the plot, Charlie is never seen as an adult in the show's nine year run. (At least not definitively: He may be one of the silent mourners at their father's funeral.)
There's also Senator Matheson, who's set up in Little Green Men as a replacement for Deep Throat. He appears only once, and is mentioned a few times, in Seasons 2-3 before disappearing. He reappeared for a single episode in Season Six then vanished completely.
Originally, Jim Davis created Lyman so that Jon would have someone to talk to, a sort of sounding board. As Garfield evolved into a more human-like character and began taking over that role, Lyman became redundant.
Garfield's Scary Scavenger Hunt on the official website features Lyman trapped in the dungeon, and in the shower (the sequel replaces him with Jon) of a Haunted House. After feeding him a muffin, he mysteriously vanishes. He also runs the bookstore on the site.
Garfield has, in fact, become steadily less reliant on its supporting cast overall, a far cry from the days of the 80's and 90's when Jon and Garfield were depicted as having fairly active lives outside of the home. Characters such as Jon's family, Irma at the diner, and Garfield's girlfriend Arlene have all steadily phased into near-obscurity. Even Odie's appearances are now noteworthy events. The spiders Garfield harasses (and vice versa) have strangely emerged as the strip's most dominant supporting characters in the 2000s.
The mystery was FINALLY solved on a four-part episode of The Garfield Show, called "Long Lost Lyman"!
The titular character of Cathy originally had a doggedly determined boyfriend, Emerson, who pursued Cathy with the same hopeless determination as she gave to Irving. He faded away after the first year or so.
In FoxTrot, Peter's girlfriend, Denise Russo, whom he met in the first year of the comic strip. She suddenly disappeared in the middle of the decade (a couple years before it went Sundays-only), but he didn't seem to break up with her (one could say it happened off screen, but at the same time we never see Peter trying to date any other girls).
And once the strip became Sundays-only in 2007, pretty much all of the supporting cast either disappeared or made smaller appearances, leaving just the titular Fox family and Jason's friend Marcus.
Shermy from Peanuts was the first character to get a speaking line in the strip, and Charlie Brown's best friend early on, but then vanished without a trace sometime in the 60's.
Mad Magazine pointed out Shermy's disappearance with "Will Success Spoil Charlie Brown?", a feature they ran several years later in which he comes back to the strip and finds everyone in it has let stardom go to their heads.
Several other Peanuts characters disappeared for the same reason, as creator Charles Schulz has admitted - they just weren't that interesting. The roster of the eventually-missing also includes Violet and the first Patty (the two random Mean Girls in the early strips) - in other words, all the initial characters except Charlie Brown and Snoopy - as well as one-note types like Frieda. Shermy was explicitly replaced by Franklin, the strip's first black kid.
After appearing in about two strips, Charlotte vanished due to all the criticism she got for going too far in her cruelty. Unlike Shermy, Patty and Violet, who at least were Demoted to Extra for awhile, Charlotte never appeared again at all. Charlotte had a lot of potential, too; her full name was "Charlotte Braun," and, as that might suggest, she was created as a female counterpoint to Charlie Brown. She was basically the opposite of him: abrasive instead of timid, over-confident instead of self-loathing, convinced the world owed her instead of convinced the world hated her. Schulz quickly learned that people liked Charlie Brown for the same reasons they hated Charlotte. He replied to one letter writer who asked him to take her out of the comic, "I will remove her, but how do you feel about causing the death of an innocent child?" (the letter included a picture of Charlotte with an axe in her head). Ouch.
Freida (apart from being an example herself) also had a cat named Faron who was featured prominently for a few months and then disappeared forever. Word Of God says this was because it wouldn't make any sense for her and Snoopy to interact as they could only communicate through thought bubbles. Charles Schulz apparently got over this as Snoopy's siblings made later appearances and he communicated with them through thought bubbles.
Just about every other character in the Prickly City strip besides Carmen and Winslow was a victim of this.
This was the case with the main characters in Out Of The Gene Pool. The strip was originally about Rufus and his friends and families. Later in the run the cartoonist switched focus to Rufus's brother-in-law and changed the title to Single And Looking. Rufus was never heard of again until a year later when he appeared in the very last strip, snarking about how he never had a proper closure.
In the comic strip Robotman, the titular character got abducted by aliens, and was never mentioned again. Eventually, the comic strip got renamed to Monty, one of the other characters who became the new main character.
Also, the strip was first about him staying with a traditional family, and much of the comedy was based on "weird urban alien hijinks" similar to E.T. or Alf. They vanished with no explanation. This was later lampshaded.
Calvin of Calvin and Hobbes was introduced to an Uncle Max, his father's younger brother, fairly early on in the comic strip's run. Max's single visit to Calvin's home was also his last, and as Watterson put it, "Max is gone." He's said that he thought inventing Max would offer new story opportunities, but realized that introducing an extra adult just intruded upon the strip's childhood setting; it'd be difficult to have Max and Calvin's parents interact without branching them off into more grown-up stories, and having Max never refer to Calvin's parents by name (a cardinal rule for the strip) felt too contrived.
Chip Dunham's Overboard had several pirate characters early on that just sort of disappeared over time. To replace them, he's increasingly relied on Talking Animal characters (dogs, mice, and rabbits) to serve as foils to lead character Captain Crow and remaining shipmates Charley and Nate.
Pretty much every character from the early days of Bloom County. Milo was the only character to last the entire run, and before it was over, even he was Demoted to Extra. Notable vanishings were Milo's grandfather and Cutter John's girlfriend Bobbi Harlow.
Which is weird because Bobbi was already well established as a foil for Steve Dallas when Cutter John was introduced to be her boyfriend.
The original premise of the strip was about Milo living in a large boarding house full of quirky residents. ALL of these people ended up vanishing, and eventually, so did the house itself.
Berke Breathed admitted that he hadn't found the strip's "center" in early comics; when Opus emerged as that center, he took focus and there was no longer a need to "try people out".
In Beetle Bailey, Beetle had a steady girlfriend named Bunny, and they had been together as the comic progressed all the way up until the turn of the century, when Bunny vanished without any explanation. It took a few years but Beetle got a new girlfriend, the famous Miss Buxley.
Before he joined the army, his girlfriend was Buzz. In 2010, a strip revealed that she was now dating his old friend Bill, another character who disappeared when it switched from college humor to army humor.
There was a homeless match seller who appeared in a number of early Alex strips. He vanished a few years into the run without explanation.
Barney Google. The star of his own comic strip from its creation in 1919, he gradually faded out in the 1950's and hasn't been seen in over half a century - but STILL gets top billing in the Artifact Title of the strip, Barney Google and Snuffy Smith. Most people just know the strip as Snuffy Smith nowadays. Oddly, the strip also went through a stretch where it was entitled Barney Google and Spark Plug, the latter being a racehorse who was also dropped in the transition to Snuffy Smith. Though Barney Google did return in 2012 as a short cameo.
In The Amazing Spider-Man, Maria Lopez was a professional rival and potential romantic interest for J Jonah Jameson. After a reboot storyline that was later retconned into a dream sequence, Maria had vanished without explanation and has never been seen since.
Early on in Pearls Before Swine, Pig and Rat got a new roommate, Leonard. The creator of the strip was hoping he'd make for some good material, but it didn't work out and he was rarely seen. Eventually he WAS killed off screen, getting his head stuck in the toilet and drowning.
In Piranha Club Ernie was going to Doris Husselmeyer's house to meet her for the first time. Another man was there too, and Ernie asked if he was going to meet Doris as well. The man said that he wouldn't, and that he was going to meet "the pretty sister," who, at the end of the strip, turned out to be horribly ugly. She was never seen again.
There was once a strip called Thimble Theater, about a woman named Olive Oyl, her equally punny named family, and her boyfriend, Harold Hamgravy. Ten years in, it introduced a sailor named Popeye who proved to be an Ensemble Dark Horse, and shortly after that most of Olive's original supporting cast disappeared.
Alison Bechdel has frequently noted just how tough making Dykes To Watch Out For was, so it's not surprising that she just plain gave up on a number of characters:
Harriet - Originally Mo's long-suffering girlfriend, Bechdel liked her enough to keep her around long after the breakup, and she transitioned to a viable secondary character. However, new characters (particularly Stuart, Jiao Raizel, Jonas, and Cynthia) and their storylines eventually took top billing, and Harriet was gradually phased out.
Naomi - Apparently, Bechdel intended her to be part of the main cast and just could never find her niche. She did a few minor things (most notably the Passover strip), was revealed to be bisexual, and finally had one or two throwaway cameos before never being mentioned again.
Thea - Handicapped (but doesn't want to make a big deal out of it), femmey, somewhat rough personality, used to be with Sydney, now with Maxine (apparently the longest-lasting, most stable couple of all). That's it. Bechdel even stated that Thea's an artist but could just never work it into the strip. Vanishes almost immediately after Madwimmin Books closes. Lampshaded in the "strike" strip:
"I thought I would be a nice two-dimensional character like the rest of you. But noooo, I just show up on my crutches every tenth episode like a damn poster child!"
Jezanna - One of the integral characters for much of the strip's run; unfortunately, she lost all relevance after the bookstore closed. Got a handful of strips and then vanished.
June - Much like Thea, she simply got lost in the shuffle. She left the strip immediately after breaking up with Sparrow and only appeared in a few cameos afterward.
Yoshiko - Ginger's artistically-minded student (and apparently a longtime friend of Lois as well). She was actually listed as a main character in one of the books. Never did anything of note and disappeared after a few strips.
Sophie - Madwimmin Books intern who had a couple of witty verbal jousts with Mo. She was another victim of the bookstore's closing.
Early on, Mother Goose in Mother Goose and Grimm lived with a male pig named Ham. He was quietly dropped over time.
British comic strip The Perishers: interesting story. One recurring character, Kilroy the tortoise, believed himself to be the reincarnation of Adolf Hitler, wore a swastika around his neck, and spoke with a mangled German accent. In 1984, the newspaper that carried the strip, the Daily Mirror, was purchased by Robert Maxwell - a Czech from a Jewish family, who lost loved ones to Auschwitz. For obvious reasons, Kilroy was never seen again.
This happens regularly. Wrestlers leave the company, which is very rarely acknowledged on the air; the sole reference will generally be in a short corporate press release stating that they and the company have come to terms on their departure and that WWE "wishes them the best in their future endeavors" — leading to the popular Fan Speak term for a wrestler being fired: being 'future-endeavored'. They may be taken off the air prior to leaving, to lower their 'drawing' value. Usually this happens to guys who work the lower matches, and so flies under the radar, but occasionally even a big name will simply vanish. For example, Sable, who was extremely popular in the late '90s, abruptly vanished from programming — because she sued the company. Similarly, Eric Bischoff was taken off the air in WCW for his inept management, and his on-air departure was never acknowledged, which made it even less understandable when he returned in April 2000.
A particularly egregious example was when wrestling's first megastar Hulk Hogan left the WWF in 1993. After losing the WWF title to Yokozuna at King of Ring, Hogan was never mentioned again until wrestling started taking on more 'realistic' storylines.
One of the worst examples of this happening was the managers of "Stunning" Steve Austin after he first entered WCW in 1991. When he debuted, he was accompanied by a brunette named Vivacious Veronica, however after a few weeks she was replaced without explanation by a blond called Lady Blossom (who was Austin's then wife and former WCCW valet, Jeannie Clark), about a year later she disappeared and Paul E. Dangerously (AKA Paul Heyman) took over the job of managing Austin.
Madusa and Col. Robert Parker both fit in there somewhere too.
When Berlyn (WCW mainstay Alex Wright, repackaged) debuted, he originally came out accompanied by three bodyguards and a pretty female interpreter named Uta who was getting surprisingly popular fairly quickly. Then Uta and two of the bodyguards disappeared about a month into the character's run with absolutely no acknowledgement.
A recent example; in late 2010, after his Face-Heel Turn, Tyson Kidd appeared on RAW with a new bodyguard, 7-foot developmental talent Jackson Andrews. Andrews, for all of his size and intimidation, was as green as grass, and after about 4 weeks, following Kidd losing a match to Mark Henry, Andrews sustained a World's Strongest Slam from Henry and returned to developmental limbo, where he would be released soon after, never to be mentioned or talked about again.
Happens a lot with valets, for instance, Carlito's temporary bodyguard-or-something, Jesús (as in "Hey-suess"), who, in Kayfabe, stabbed John Cena in a night club. He then faced Cena in a street fight at a PPV, which resulted in Jesús getting beaten within an inch of his life and never being mentioned afterwards.
If not for CM Punk's throwaway lamentations, those who don't check WWE corporate statements would probably be ignorant about guys like Festus/Luke Gallows, Mike Knox and Vladimir Kozlov getting 'future endeavored'. Nor would they be aware of John Morrison, Melina, Gail Kim or the Bella Twins just up and leaving.
Or, in the case, of the Bellas, returning out of nowhere either.
Possibly justified example in Chris Benoit after it was discovered he had killed his wife and son before committing suicide. DVDs prominently featuring him were discontinued (some permanently, such as his biographical release), commentary for certain matches featuring him were edited, and his name was removed from many pages on WWE's website. As of late, they've steadily begun reversing this course, but never so far as to even indirectly mention him on TV.
Remember the guy who won Tough Enough? Andy Leavine? A few videos aired for hyping him up, however they stopped and he was quietly released months later, never to be mentioned again.
Warhammer has entire races that silently disappear between editions. What happened to the Fimir?
They made a recent appearance in the Graham McNeill Sigmar-era novel Empire. The 'mist daemons' are never definitively labelled as Fimir but it is very clear what they are supposed to be.
The Chaos Dwarfs in the Warhammer Fantasy world have also simply disappeared. To the point that even though they are still included in the last official Blood Bowl rulebook, they are the only official race not in the computer game.
They were mentioned, repeatedly, in the second edition of the role-playing game.
They are still mentioned quite a bit, both as a source of equipment for the other chaos factions and Ogres and as the origin story of the Black Orcs.
It seems likely, in-universe anyway, that there's simply too few Chaos Dwarfs to make a full army out of them, even with Hobgoblin and Orc slaves supplementing them, as the scarcity of their race was something mentioned repeatedly.
Chaos Dwarfs have seen a resurgence as of late 2011, given that Forge World has started producing a line of them in Warhammer Forge. Whether or not they'll return to being a mainstream army is yet to be seen.
Bull Centaurs have it even worse. Chaos Dwarfs have three models being consistently produced as Hellcannon crew (admittedly without the stylish headgear of the classic Chaos Dwarf range). Bull Centaurs have vanished entirely.
In Warhammer 40,000 the Squats vanished as well, partly for low sales but mostly because they were too silly/campy in a setting that was becoming Darker and Edgier. Word Of God has usually been "the Tyranids ate them all" (supported by the "Abhuman" section in the 6th edition rulebook) but they have occasionally tried to claim "they never existed". Blame Chaos, perhaps.
The same happened earlier on to several models in the 40k range with the simplification that happened in the 3rd and 4th editions. However some of them have been making a comeback in recent editions, most notably Bjorn the Fell-handed and the infamous Jokaero.
William Shakespeare's Romeo and Juliet: Benvolio is an important character up until the end of act III. After that he's never seen or mentioned again. In some versions of the story he shows up at the very last scene but in most he just disappears. What happened to him? Did he decide to leave Verona? Or did Shakespeare just forget/ignore him?
Reynaldo, in Hamlet, appears in one scene being given detailed instructions to watch Laertes and report his habits and misdeeds. He leaves and is never heard from again, even after Laertes comes back.
While Mario and Donkey Kong have both ascended to stardom since their debut game, Pauline, the girl they fought each other for the first place faded into obscurity as Princess Peach took over her role as Distressed Damsel in the Super Mario Bros. games. She did reappear in Donkey Kong '94, only to disappear for another decade until Mario vs. Donkey Kong 2, in which Pauline's relationship status to Mario was demoted from "girlfriend" to "friend".
Donkey Kong Junior hasn't appeared since Game and Watch Gallery Advance.
Though, this depends on which continuity you subscribe to. According to Rare, the Donkey Kong seen from Donkey Kong Country on forth IS DK Jr., while Cranky Kong is the previous DK. Donkey Kong Country Returns retcons it, however, to current DK being Cranky's grandson, meaning that DK Jr. really has been MIA ever since.
Stanley, from Donkey Kong 3 also vanished from the series appearing only in some cameos like WarioWare or Smash Bros., it's unclear, but it's said he's also the protagonist from the Game & Watch Greenhouse and it's also rumored that he is Mario's cousin.
Poochy had an entire level designed around him in Yoshi's Island, but has been absent since Yoshis Story. (He remained in the remake of Yoshi's Island, but was absent from the new levels.)
Plum, Charlie, Sonny, Harry, and Maple, human characters who are playable in Mario Golf for the Nintendo 64. They have not made a single appearance in any game since, unless you count Plum's cameos in Super Smash Bros. Melee and Brawl as a trophy and sticker respectively. Not to mention that that's five out of fourteen playable characters.
Toadette also seems to be a short-lived character, first appearing in Mario Kart: Double Dash, then making periodic appearances in Mario games until Mario Super Sluggers nearly five years later, then never appearing again. After another five years, she reappears in Mario Kart 8.
Fawful, who appeared in the first three Mario & Luigi games, is mysteriously absent in Mario & Luigi: Dream Team. The reason for this could possibly be his explosive defeat at the end of the third game, but considering almost every Mario boss blows up, his absence is still a mystery.
On a related note, Mario RPG characters in general rarely reappear in other Mario titles. Exceptions include Goomba King, Baby Peach, and the Star Spirits, although in Baby Peach's case her debut in Mario & Luigi: Partners in Time was likely coincidental. Paper Mario: Sticker Star is notable for not returning any previous Paper Mario characters and only using characters from the main series, introducing only Kersti as a new character.
On the "explode" subject, this is a common misconception. At the end of battles is when the bosses explode, but their explosion is just a flashy way of signalling their defeat and the end of the battle mode, and is only to be taken as canon if the boss has vanished when Mario exits battle mode (like Elder Princess Shroob). Bosses who explode outside battle mode are the only ones that actually count, and none of them return after that (except Petey Piranha, and as he's in the Koopa Troop Bowser probably revived him as he usually does). Swiggler, Sunnycide, Shrooboid Brat, Commander Shroob, Elder Shrooboid, Princess Shroob, Scutlet, Kretin, Dark Bowser, Fawful, Grobot, Torkscrew, Mammoshka, Pi'illodium, and Antasma all blow up outside the battle (even after doing so inside it), are never seen again, and are most likely dead.
Zhuzhen and Halley from the original Shadow Hearts are unmentioned in the sequels. This may be somewhat justified, though, in that the former returned to China while the later left for America. The Valentine family gleefully subvert this.
It may have been just a regular dream, but Wart was killed as well. His corpse was even tossed around by the Subcon and turned into fried chicken.
Dynamo in Mega Man X 5 and X6. The only antagonist in the series to remain alive and intact (that is, not coming Back from the Dead), he worked for Sigma in X5, returned in an arbitrary cameo in X6, and vanished off the face of the earth.
Similarly, Douglas only appears in X5 and X6, then disappears after that. Lifesaver only appears in X5 (granted, he wasn't very popular due to his Nice Job Breaking It, Hero action). Dr Cain was last seen in X3, last mentioned in X4, and gone after that.
The Updated Re-releaseMaverick Hunter X has Dr. Cain dying in an attack on the Hunters' headquarters; whether this is a Retcon or not remains unclear.
In the Mega Man Star Force series, Pat Sprigs is a major character in the first game, cameos in the second, and vanish in the third. What's frustrating is that the game itself acknowledges that it still has plot points to wrap up regarding him. Pat also disappears from the anime as well, only to make a very minor cameo at the end of the final episode.
In Xenogears, Billy's dad Jessiah disappears (much like most of the game) when Disc 2 starts. At least, from the storyline, technically he is still around as he is is the gun/bullet in one of Billy's gear's special moves. Oh, and Kaiser Sigmund too - despite the fact that an early Disc 2 plot point would probably have him heavily involved. Disc 2 has a much tighter story focus than the first disc, playing more like an interactive novel than a standard RPG, and the planned storylines for both characters may have gotten lost in the same budgetary constraints that are rumored to have caused the gameplay shift.
Parodied in Banjo-Tooie, where the face of Tooty, Distressed Damsel of the first game and kid sister of Banjo, appears on a milk carton in Cloud Cuckooland, one of only two appearances of Tooty in the game (the picture of her in Banjo's house from the previous game is still there; in fact it's one of the few things in the house that is not significantly damaged or destroyed). Rare obviously never saw her as anything more than a walking plot device for the first game, and thus hand-waved her absence circa Nuts and Bolts, saying she was hauled off by the "Rubbish Video Game Characters Police".
Brentilda completely vanished as well. Her only appearance is in a portrait in Pawno's Emporium in Jolly Roger's Lagoon.
Every surviving character from Metal Gear and Metal Gear 2 that didn't make the transition into Metal Gear Solid series was forgotten by default: Ellen Madnar, Diane, Jennifer, Holly White, Yozef Norden Johan Jacobsen, George Kasler.
Subverted with Meryl, who vanished without explanation, except for an implied reference an optional conversation in MGS2 in which Snake says he's had enough of tomboys. Players were left to assume that the ending of MGS1 in which she died was canon, until she showed up in MGS4.
Surprisingly enough, this is Averted with Dr. Pettrovich Madnar in MGS4. While he doesn't make an actual appearance, it's explained that he saved Raiden's life behind the scenes, even though he hadn't been mentioned at all in the last games, and him being the original creator of the first Metal Gear had long since been retconned.
Many Sonic characters like Ray the Flying Squirrel, Mighty the Armadillo, Bean the Dynamite, Bark the Polar Bear, Nack the Weasel (a.k.a. Fang the Sniper), Tails Doll, G-Mel and Metal Knuckles, have been subject to this.
Since about the time of Sonic Unleashed, more recent and/or once-major characters have been set aside in favor of simply having Eggman, Tails, and Sonic. This may be in response to the criticisms for the series' Loads and Loads of Characters.
Soul Calibur V is notable for having a lot of new characters at the expense of losing some old faces, including, rather infamously, popular faces Talim and Zasalamel as well as Rock, who have literally disappeared without a trace. At least Cassandra had her fate told in an artbook and the fate of Seong Mi-Na, Yun-seong and Setsuka were mentioned later on (With Setsuka having been Patroklos' teacher at one point) but Talim, Zasalamel and Rock have seemingly vanished off the face of the earth with no mention whatsoever from artbooks or Word Of God as to what happened to them, almost as if they never existed. This has contributed to SCV's status as a Base Breaker amongst the fans.
Touhou's transition from PC-98 to Windows is either a Continuity Reboot or the single largest case of this ever. Only four characters ultimately survived the changeover out of forty or so, losing fairly major characters like Mima and Genji.
In The Elder Scrolls, General Warhaft. Leader of the Imperial Legion, wrote two of the in-game books on armour and fighting, imprisoned along with the Emperor by Jagar Tharn... but he never is mentioned after Arena, except for in the aforementioned books. He goes unheard of in Daggerfall, Battlespire and Morrowind, and when the player visits the Legion headquarters in Oblivion, he's replaced by Commander Adamus Phillida, with no word on what happened to him or where he is now.
In a large-scale Chucking, the cities of Sutch, Artemon, and Mir Corrup were mentioned as being in Cyrodiil in several prior games. When Oblivion comes around, and we actually get to visit Cyrodiil, the entire cities are gone. The developers admitted they never had time to add them into the game (a semi-canonical explanation was made for Sutch, though - apparently, the city was ceded to Hammerfell as part of the peace settlement following the events of Redguard. Which only left the problem of why Sutch had been implied to have been a part of Cyrodiil after that point, of course).
The protagonist characters have a semi-enforced and downplayed variant: the following games do acknowledge what happened in the last one, and they do touch upon the character you played, insofar as it would be known to the public, but details that would vary from play-through to play-through are, for the most part, strenously avoided, presumably to avoid invalidating people's play-throughs.
Recent Word Of God on the events of Skyrim tries to explain this by saying "all the quest chains present in the game happen, but not all are necessarily done by the Dragonborn." This could also be taken as their attitude towards the protagonists in previous games.
Almost half the kids in the Backyard Sports series. But the series never explains why anything happens anyway.
Simon the Sorcerer 3D has a strange character called Jar Nin whom you accidentally kill at the beginning of the game. Towards the end of the game it turns out that you have to resurrect him because you need him on your team. But when you do, he does exactly nothing and even vanishes shortly after, never to be seen or mentioned again.
Not characters per se, but every creature from the Xen borderworld in the first Half Life 1 - apart from the standard headcrabs (and zombies), the barnacles, the Vortigaunts (now as an ally), an ichthyosaur as a cameo, and the leeches (who are now invincible barriers to the ocean) - somehow vanished from the cast list before the start of Half-Life 2.
Stranger still, Barney Calhoun seems to be suffering from this as of Episode 2.
For that matter, with the exclusion of Barney, pretty much every major character from the first game's expansions (Shephard from Opposing Force, Gina and Colette from Decay, and Rosenberg from Blue Shift) disappeared entirely between the first and second game. Considering the circumstances, this could be justified.
Leaf, the female protagonist of Pokémon FireRed and LeafGreen. She was supposed to appear in Red and Green, the first Pokémon games, as a female protagonist, but due to a lack of space, she was taken out. She was then redesigned for FireRed and LeafGreen years later. She was going to be a model for Pokémon Battle Revolution, and has appeared in at least five official artworks, but since has long been forgotten by Game Freak.
She also has only had counterparts in two of the many manga, and has not even been referenced in the anime.
Most characters in the Wario Land series just vanished without a trace after the original games they were in. Captain Syrup returned in Shake Dimension, after a ten odd year gap between appearances, but God knows what happened to Rudy the Clown after he returned in Dr. Mario 64...
This phenomenon is also seen in Jak and Daxter. Gol and Maia are the duo's first major baddies, and after their defeat in the first game a return is hinted at by the Green Sage. However, the series decided to go Darker and Edgier and thus the rogue Sages were "chucked" out.
The second game introduced us to Brutter, the leader of the local Lurkers who befriends Jak and Daxter. At the end of the game, he seems to be working for Ashelin as captain of the New Krimzon Guard, but he is nowhere to be seen in Jak 3. Admittedly, Brutter does make a short appearance in the Daxter spin-off, but since that game is set before Jak II it doesn't explain what happened to him between Jak II and 3.
The second game also had the Crocadog, a Mix-and-Match Critter that Jak seemingly adopts as his pet in the end. He is never seen or referenced after Jak II.
Jak's uncle in the first game. While Jak was born in the future and thus he can't be his real uncle it feels a bit weird how after delivering the orbs to him he is never mentioned again. You'd think that he'd care a bit more about Jak's adventuring since he probably raised him.
Ottsel!Veger is adopted by Kleiver as a sidekick, yet vanishes entirely by Jak X and is never mentioned again. His fate is unknown, but hopefullyveryunpleasant.
Ys: Lilia, after being Demoted to Extra, disappears from the series after IV, as well as several other major characters from I and II. Subverted with Dogi, who is oddly absent from V, but returns in VI, as does old man Raba. Also, what happened to Terra between VI and Seven?
A handful of the characters from the very first Street Fighter are nowhere to be found. At first Ryu, Ken, and Sagat were the only ones to return, then the Alpha series brought back Birdie, Gen, and Adon. Eagle made an appearance in Capcom vs. SNK 2: Mark Of The Millennium. To this day, however, Geki, Retsu, Lee, Mike, and Joe are all but disowned from the series (well, maybe not Mike, who is widely hypothesized to be "Mike Bison"/Balrog).
The comics have had some fun with these. Lee reappears in the Sakura Ganbaru manga as an opponent for Sakura, and in UDON's comics, reappears to challenge Fei Long and is stated to be the uncle of Yun and Yang. Also in UDON's comics, Geki attempts to assassinate Gen, and in the Ibuki miniseries, "Geki" is retconned to be the name of a ninja clan, not an individual, which has a rivalry with Ibuki's clan.
Most of the Street Fighter III cast would qualify, too. The popular ones would go on to appear in other Street Fighter games (Yun, Ibuki, Makoto, Dudley) and crossovers (Alex, Yun, Urien, and Hugo—who is technically not from SF III, but still counts) but most of them were lucky to even appear as cameos or passing mentions in character storylines. Part of the problem, it should be said, is the long lull in Capcom fighting game releases prior to Street Fighter IV.
The characters who debuted in Street Fighter EX belong have never appeared in another Street Fighter game outside of the EX series. The fact that the characters are joint-owned by Capcom and developer Arika may have something to do with it (though a few have made the occasional cameo in other Arika games, and the company started work on a game featuring the EX-only cast.)
One of the most unusual cases within the EX series was a character called Hayate, a young Japanese swordsman. He appeared as a newcomer in EX 2, but was mysteriously removed from the updated version of the game. The PS1 port returned him to the roster as a secret character, but after that, he never appeared again (and was the only character from EX 2 to not return for EX 3). There was a persistent rumour that he had been killed off between the two games, but no, he simply vanished entirely without a trace.
A potential explanation for Hayate is that Capcom removed the character because they couldn't sell EX 2 in Korea due to that country's hatred of samurainote The same reason Namco created Arthur, a blond British totally-not-a-samurai, to replace Mitsurugi in certain versions of Soul Calibur; he does stay around in another way, as his Super Combos were given to Garuda as his Meteor Combo.
In Apollo Justice: Ace Attorney, where did all of Phoenix's friends go in the past seven years? The only characters from the first three games that show up are Phoenix, Ema, Payne, and the Judge (and, in flashback, Gumshoe and Mike Meekins).
Maya is mentioned, as is Mia, just not by name. Phoenix at one point refers to a "kid" he knows who sends him Samurai series videos tapes and he again mentions a "Girl" he once know who Trucy reminds him of. Guy Eldoon, the noodle saleman, even refers to Maya at one point saying that Phoenix used to frequent his noodle stand with "That assisant girl" back when he was an attorney. Examining "Charley" in the office, prompts Apollo into talking about how Phoenix mentioned his "Chief" once.
Ema also references Edgeworth when informing Apollo that prosecutors should be "simmerous" rather than "glimmerous."
This is probably done to not spoil any cases from previous games.
Mortal Kombat: All of the characters from Special Forces and Mythologies: Sub-Zero who haven't appeared in a Fighting Game before (Sareena had a playable appearance in a portable version of Deadly Alliance called Tournament Edition) didn't made the cut for Armageddon.
Except Sareena's two partners in Mythologies; they appear in Konquest Mode of Armageddon as minibosses.
Tremor later resurfaced in playable for the PS Vita release of Mortal Kombat (2011) due to immense fan demand, however.
In World of Warcraft, Calia Menethil, Heir to the throne of Lordaeron, disappeared without trace shortly before Warcraft III. It is speculated that she has taken the name of Calia Hastings and is currently working for the Stormwind SI:7 spy agency, but this is based solely on the One Steve Limit.
If Calia Hastings was the missing Princess of Lordaeron, she's either dead, or double-dipping in this trope since the destruction of Theramore just prior to Mists of Pandaria.
A Q&A with Warcraft's Creative Devs had them answer all "where are they now" questions with a general "we have plans and don't want to spoil them" answer.
In the RPG books, Brann Bronzebeard lampshades this, briefly mentioning that he's not sure where Calia is and that he'll have to look into it.
Also a large number of NPCs in World of Warcraft: Cataclysm. Overlaps with Never Found the Body in some cases.
The black dragon Sabellian, as the only one of his race who doesn't seem to have a problem with the player races, is conspicuously absent from all the events surrounding the return of his father Deathwing, the destruction of the rest of the black dragonflight as incurably corrupted, and the birth of his uncorrupted brother Wrathion. Possibly he decided he wanted no part of the whole thing and just stayed in Outland. It was later confirmed that Sabellian is still alive and Wrathion simply doesn't know about him.
Though Tawna does reappear as a playable character in the DS game Crash Boom Bang. The game manual states that she's dumped Crash for Pinstripe Potoroo.
LEGO Island was hit with this hard. Let's see, we had Captain D. Rom, Enter & Return, the Funbergs, Polly Gone, Studs Linkin, all of the flying Legondos (excluding Jack O'Trades), and the two workers.
Dynasty Warriors 6 was notorious for cutting some of the roster and relegating twenty-four of the remaining forty-one characters to "Free Mode only" (having no Musou Mode storyline and cutscenes, though its PS2 re-release converted six of them to Musou Mode, for a total of twenty-three Musou Mode characters and eighteen Free Mode only), but in Dynasty Warriors 7 when all of them were brought back except Zuo Ci and Pang De. The former was an inconsequential Daoist mystic, but the latter a notable warrior who'd participated in several key battles and brought his own coffin to his final military campaign ("win or die," literally), only to not be mentioned at all in the game, which KOEI explained was due to "certain storyline constraints" (namely, that they didn't have room for him in the direction they were taking the story). In a subversion, however, Pang De reappears in Xtreme Legends, which made it look like the trope was a harbinger for his eventual return.
The heroes of Might and Magic 3 disappeared without the games ever quite explaining how they went off-course, or even if they did. They just... didn't arrive on XEEN, and when they next showed up (in Might and Magic 7), all they said was that they'd been looking for the Ancients for some time. Of course, they did return, so it isn't a clear-cut example of Chuck Cunningham Syndrome.
General Vladimir, who was an important supporting character in Command & Conquer: Red Alert 2, is nowhere to be seen in Yuri's Revenge, the game's expansion pack.
Dragon halfling Halfas in Dragon Valor is nowhere to seen chapter five, despite the fact that his actions drive the plot of chapter four (either killing the Sacrificial Lion or cursing the character to die in a month).
The Wave Race series has the four races from Wave Race 64 appear... except for Miles Jeter, who just didn't come back without an explanation.
In Advance Wars: Dual Strike, Flak and Adder are completely absent from the story, though they are playable after you beat the campaign. This may have been because of how similar they are to newcomers Jugger and Koal, who have actual bearing on the story.
Loading the first pre-made neighbourhood included in The Sims 2, the player is greeted with a short slide show which informs them that this particular neighbourhood's story picks up twenty-five years after that of the default neighbourhood in the first game. Members or descendants of four of the five original base game families are there (as well as one or two of the families from later expansion packs). But Chris Jones and Melissa Smith (a.k.a. Chris and Melissa Roomies), who were at least as important and popular with the fans as the other characters - they're simply not there, nor do they even turn up in later expansions as some others eventually did.
Final Fantasy VI: Most of the first half of the game is spent working with the Returners, including the old man Arvis who's the first non-Imperial you speak to and Banon, their leader. You last see the two of them in the ruins of the Imperial capital, Vector. Kefka's ascension and the destruction of the world might have killed them, but they're simply never seen or mentioned again.
In the Kingdom Hearts series, we've got a whole world who disappears completely from the series: Deep Jungle. This is justified, as Disney could no longer secure the rights of the franchise. In the dreams at the beginning of Kingdom Hearts II, when Jafar mentions that Sora's found a Keyhole, the resulting scene is Sora sealing the one for Agrabah (after Jafar's defeat), when he actually said it after the one for Deep Jungle is sealed.
Elora from Spyro the Dragon was a major character in Spyro 2: Ripto's Rage! but only got a cameo at the end of Spyro: Year of the Dragon. After that she's suspiciously left out of every other title in the "classic" line, aside from popping up on a trading card in Spyro Orange, despite the fact the others (even Bianca) became Ascended Extra's. There were plans on include her in two games but she was excluded.
In the ending of the Decepticon version of the DS game for the 2007 Transformers movie, the player's last words imply that Megatron is the only Transformer still alive. While all of the Autobots and most of the Decepticons are killed on screen, Brawl is never seen again after he kills Ironhide.
Euchre from TwoKinds just seemed to be forgotten about. After Traces battle with a Neutal possessed Flora, he is never mentioned again despite him being a rather important and seemingly powerful character who was in leagues with the Master Spy.
He might simply Master Strategist in a magical disguise.
In truth, he IS a Keidran that can disguise into a human down to the genes and with what seems to be some kind of double personality syndrome, since he helps Keidran while undisguised while leading the persecution in disguise. He has a half-human/keidran changeling daughter.
Sara from Questionable Content was a barista at the Coffee of Doom who had a crush on Marten for the first few strips. She seemingly disappeared early on, when the focus shifted to Faye and Marten. This has been subject to a Lampshade Hanging on more than one occasion. The 'official' explanation for her disappearance is that she was eaten by an allosaurus, but really she was just a boring character.
Is often lampshaded and subverted. Members of the supporting cast regularly disappear - often for extended periods of time - without warning and are later given explanations when another character wonders why they are gone. Most (with Sara being one of the only exceptions) will turn up again up to 500 pages later.
In El Goonish Shive, some of the side characters have fallen into this. And of course, let's not forget Lord Tedd, hinted in the past to be the Big Bad of the entire strip, has not been seen in years real-time.
Dan Shive said he introduced the character too soon, which is why it vanished. However, it looks like Lord Tedd may be coming back.
Early in Kevin & Kell, Lyndesfarne was friends with a turtle and an armadillo, the gag being that they were the only three herbivores who could hang out at the mall food court. Conina the armadillo is also at the school dance, and then we never see either of them again.
Now that Dresden Codak has gone from Kim being a teenage Mad Scientist living in a big house just outside a city on the Pacific coast to being a penniless mad scientist in her early twenties living in a small room in a Vast Bureaucracy, it looks like we won't be seeing anything more from Alina, Dimitri and Tiny Carl Jung for the forseeable future.
Pv P does it so much it should be called Kurtzing. The entire cast from Samwise except for Skull, Francis' gaming troupe, Skull's gaming persona who later became his own character, Jade's former staff from when she made a feminist magazine, Jade's High School best friend, Robbie's former best friend Jase , Reggie who was Miranda's blind boy-friend, Miranda who was Reggie's hot girl-friend(redacted, though she was brought back by a guest strip so Kurtz wouldn't have brought her back if not for that strip so it doesn't count so HA), Miranda's big dumb boy-friend(whom she presumably left because he wasn't dumb any more), a talking arcade machine, Newt-boy, a funny talking rat, Francis's robot,Skull's cousin Sheckie, Sheckie's girl-friend, a divorced woman who was implied to be a recurring character,Cole's entire family, the game-store witch, and the giant Panda. That's more than 20 characters that fit this trope.
Gwen almost fit this until she became in expy in Kurtz' other strip "The Trenches".
Sonichu has this all over the place, as new characters were created to be analogues of people who tormented the creator in Real Life. Most characters just disappear, getting squeezed by the Kudzu Plot.
Shauna from Bad Machinery had an older brother, the only explanation of this disappearance is, in answer from John Allison to a question about this on Tumblr, "Chuck Cunningham’d"
Drake, FemAdmin, and Sagan of the Hijacker Trolls from the Bronyism blog all seemingly disappeared without a trace since Nightmare Nyx's reclaiming of Bronyism. Subverted as Trollvorlord gives an explanation for the absence of the other members of the team later on in the story.
Tiny Toon Adventures brought Bosko, Honey, Foxy, Foxy's girlfriend and Goopy Geer back for cameos, in which they were hailed as talented veteran cartoon stars. Later, an episode of Animaniacs had Buddy make an appearance, but it was a lot less complimentary toward the character in question (turns out Yakko, Wakko and Dot were created just to spice up his notoriously boring cartoons).
Bosko, the original Looney Tunes star, very rarely makes appearances in modern Looney Tunes artwork, and hasn't appeared in any cartoons since his redesigned cameo in Tiny Toons. Understandably, this is due to his roots as a blackface character making him an unacceptable character to put into the mainstream today. It dosen't help that his esoteric nature compared to the mainstream Looney Tunes (due to his cartoons being off the air since the 80's), not to mention his vague personality, do not make him a popular character among fans.
Bimbo the Dog from the Betty Boop cartoons. In the early shorts he was meant to be Betty's boyfriend, but come 1934, and the Hays Office objected to an interspecies relationship, forcing Fleischer Studios to abruptly drop Bimbo. He would never be seen again in the series.
Star quarterback Brick Flagg from Kim Possible showed up here and there, but he sort of vanished after a while. Although his no longer appearing was eventually justified at least for the last season, he graduated by then. He wasn't exactly the brightest bulb when off the football field, and it was mentioned that he'd finally graduated after being held back a few years. (He even votes for one of his opponents during the school election. Not that it mattered much.)
After the rights to Thomas the Tank Engine were acquired by HIT Entertainment, and some of the original producers left the show, several semi-regular characters, such as Duck, Oliver, Boco and Daisy, were dropped.
Even outside of the many incidental cutaway characters, Family Guy has a few.
Brian's gay cousin Jasper, who used to appear a couple of times per season, disappeared after the gay marriage episode.
Jasper appeared in the episode "Brian's Play" talking with Brian on Skype.
Joe Swanson's own children seem to disappear without a trace. Kevin Swanson appeared in the first 3 seasons, then just disappeared for years, though he had a few non speaking cameos. Years later after his last speaking role Peter questioned about his disappearance out of curiosity. Joe explained Kevin died as a soldier in Iraq with hardly any emotion. Seth MacFarlane felt Kevin was not a very interesting character to write for. Kevin is brought back as MIA in a new episode.
Parodied in Spies Reminiscent of Us when Chris enters in an exchange program to be replaced for an Elephant (don't ask). at the end of the episode Brian stated that it was a joke for the episode.
In Carol Pewetershmidt's first appearance she had just given birth to a baby boy, in her recent appearance he is nowhere to be seen.
Chris was set up to be with a girl named Anna in Long John Peter but, after that episode, she's never mentioned again and Chris is seen trying to get with other girls after that. That also happened with Herbert's niece in the Valentine's Day episode.
Nurse Gollum from Season Two (other than a voiceless cameo in "Freak Strike"). However, there's a good explanation for why she was removed from the show.
Dr. Mephesto and Kevin. They were main characters in the first 3 seasons, but disappeared early on in the fourth. One of them DID, in fact make, a one-off apperance in 201 but has not been seen since. Parker and Stone have stated, however, that they grew tired of Mephesto and had wished they'd written him off completely in season 4.
Some of the children's parents that aren't Stan, Kyle, Kenny, Cartman, Butters, Token, Wendy, etc, have been replaced with different people.
Midget Wearing Bikini and other joke news reporters seen in the earlier seasons were phased out in favor of just using "Tom" or parodies of actual reporters.
Mephesto's son Terrance was introduced as The Rival to the four boys, along with his sidekicks Bill and Fosse. Terrance quickly faded into the background, as did the other two. The three are still occasionally seen as background characters, but lack their signature thick eyebrows. Craig, Clyde, and assorted other boys now play the part of the rivals to the main four.
Mr. Wyland, the substitute teacher.
Officer Barbrady: Effectively replaced by a full police force around season 7, though he is still brought back for small appearances every now and again.
Lampshade Hanging in "Cartman's Incredible Gift" when Ms. Crabtree is murdered by a serial killer.
Lou: "I owe it to that victim over there! I know she hadn't been in any recent episodes, but DAMMIT, she deserved better than this!"
Damien hasn't reappeared in years (aside from background cameos in the gymnasium at times, or being seen on a TV in "Tsst!") despite his father making numerous reappearances.
Nurse Goodly (the nurse with no arms from "Cartman's Mom Is Still a Dirty Slut") hasn't made a reappearance in scenes taking place in Hell's Pass Hospital.
Lampshaded in the second season of Freakazoid!. Lord Bravery and the Huntsman are upset about their sequences being trimmed down to nothing in the second season and want something to do. Freakazoid makes them wash his car and that's the last we ever see of them.
Ironically, Freakazoid's alter ego, Dexter Douglas is only seen twice in the second season and never shows up again.
Remy Buxaplenty, rich bastard and Juandissimo's godchild on The Fairly Oddparents, is an odd example of this in that he is written out of the show at the end of his first appearance. Three seasons later, apparently due to viewer demand (and because he was one of the creator's personal favorite characters), he returns as a recurring antagonist to Timmy for three more episodes. After the third one, though, he's not mentioned again, not even in Juandissimo's subsequent appearances.
Also, back when Mark Chang was Timmy's enemy he had two friends on Yugopotamia named Jeff and Eric. They haven't appeared recently, not even in an episode that had Mark going back to his planet temporarily.
On Space Ghost Coast to Coast, much of the Council of Doom disappeared without a trace. The most obvious examples are Metallus and Black Widow. Lokar disappeared after "Waiting for Edward", and after "King Dead", Tansut was never seen again.
The Creature King suffered this the worst. He was closest thing the sixties series had to a Big Bad. He was the main head of the Council of Doom and fought Space Ghost more times than any other villain. Yet he never appears in Coast to Coast, unless you count stock footage from "Jacksonville".
The Simpsons: After The Movie and a brief appearance in the opening of the 19th season premiere, Colin was never seen again and Lisa is back to being single. Yeardley Smith actually voiced her annoyance at this, arguing that Lisa deserves "to keep this one."
Lionel Hutz and Troy McClure were both retired after their voice actor Phil Hartman's untimely death. Since 1998, they've disappeared from Simpsons canon (with the very occasional exception of a crowd scene). Hutz's role as the Simpsons' incompetent family lawyer was taken by 'Old' Gil Gunderson.
Early episodes had two - almost identical - characters called the Weasels do Nelson Muntz's bidding. Sometime around the third season, they disappeared and Nelson became friends with the Jimbo, Dolph and Kearney trio. The producers explained on the DVDs that six bullies felt like too many.
Homer's half-brother Herb seems to be this as well. He made appearances in two early episodes, then never appeared again. The series occasionally will quip about this, such as once when Homer makes a passing reference to "my seldom-seen half brother Herb."
Herb makes a speaking cameo on Homer's answering machine in Season 24's "Changing of the Guardian" in which he reveals that he is poor again.
The secondary Channel 6 newscaster Scott Christian was quietly phased out after Kent Brockman became recognised as the much funnier character. Ironically, a running gag was suggested that Christian would always be covering for a perpetually absent Brockman, despite the Action News show being named after the latter. One instance of this was trialled in season 1's "Krusty Gets Busted", but was soon rejected, and Brockman does actually appear later in the same episode.
Serak was in the first Treehouse Of Horror along with Kang and Kodos, who appeared in all subsequent Treehouse Of Horror episodes, but Serak didn't. Perhaps this was as James Earl Jones could not be gotten back to voice him.
One episode have the Simpson family adopt another dog, She's the Fastest, as Santa's Little Helper fell in love with her, and they have puppies together. She mysteriously vanishes and is never mentioned again.
Herman, first seen in Bart The General, was supposed to be a recurring character, his gimmick being that each time he showed up he'd give a different story of how he lost his arm. Aside from a few cameos, he's never been seen again, and how he lost his arm was resolved in a flashback episode.
Several recurring characters in King of the Hill just disappeared over time like Eustace and his geeky son Randy, who were rivals to Hank, Bobby and their friends in the earlier episodes but they vanished over time too. Bill's iguana Lenore only makes a one-episode appearance, and his girlfriend Laoma, who was Kahn's mother. A season finale episode ends with her living with Kahn and her and Bill in a relationship, but come the new season she's inexplicably gone. The writers apparently wanted to keep Bill alone and miserable.
In the episode in which Bobby breaks up with Connie, he meets a new girl named Debbie at the mall. They get along fine and are set up to be a couple; come next season she is never seen nor mentioned again and Bobby is back to being single. This happened quite a few times, actually: Bobby would meet a new girl who clearly liked him and they are seen together at the end of an episode. Invariably the girl is never seen or mentioned again.
Theres also the blonde kid Garth, who appears in the Straight Arrow episode and is implied to be Boomhauer's illegitimate son.
In the second episode, "Square Peg", Peggy is seen talking to several other women on a bench at a Little League game. Come the next episode, they have vanished and Peggy's only friend is Nancy. This may have been a retcon for later episodes that had Peggy worried that she didn't have enough female friends.
Those women do appear in the episode in which Khan and his family move in three episodes later but as mentioned previously they don't appear again after that.
Those women appear again rather infrequently and at times not all together, one episode in season 2, Peggy's Turtle Song features them delivering a very bizarre Laughing Mad moment.
In some of the earlier episodes of Spongebob Squarepants, Spongebob had a pet scallop in a bird cage above his bed. He was never seen interacting with it, though, and during the middle of the second season it vanished. This was referred to in one of the video games when in Spongebob's room when you click on the cage, he says something along the lines of "That's where I kept my pet scallop, I think he ran away".
Which is weird, in that it has been seen in later seasons, too.
Also Bubble Bass, who appeared in a couple episodes back in season 1 but has never been seen or mentioned since.
Apparently Bubble Bass was placed on a very long bus ride, because he had an appearance in the Season 8 episode Plankon's Good Eye.
Several characters in The Animals of Farthing Wood who weren't killed off, but simply disappeared in Season 3. this includes Fox and Vixen's son Friendly, Kestrel, and the surviving blue foxes aside from Ranger.
Friendly made a brief appearance in the second episode of Season 3, then was absent for the rest of the series without explanation. Word has it that the show's producers didn't like him and requested that he be dropped from the show. Kestrel's disappearance is actually consistent with the original novels, in which the character simply stops appearing around the fifth book in the series, with no specific departure arc.
Scrappy Doo from Scooby-Doo, aside from parodies and the live action movie (which doesn't really count) has not appeared in the series continuity since Scooby Doo and the Reluctant Werewolf (1988). This is mainly due to his... well, beingTheScrappy.
In the original run (1991-94) of Rugrats, two slacker teenagers named Larry and Steve were seen from time to time with a different job in every appearance. After the show's hiatus they disappeared, in a much later episode Larry appeared as a doughnut salesman and is never seen again.
Timmy McNulty and his siblings also disappear from the series too, sometime around the prelude to Rugrats in Paris and the introduction of Kimi Finster.
In the Jumanji cartoon, the villainous "Stalker" character was introduced in the sixth episode, who looked somewhat like the Grim Reaper. The other villains feared and worked for him, which seemed to be setting him up as the main antagonist of the series. Unfortunately, he only appeared in two episodes and never reappeared, despite the ending of both episodes hinting at a reappearance.
In Walter Lantz's The Beary Family the family originally consisted of Charlie (father), Bessie (mother), Junior (son), Suzy (daughter), and their pet goose, Goose. Early into the series Goose disappeared, then eventually Suzy was dropped without explanation.
In The Blue Racer the main character chased after a racially insensitive Japanese Beetle (yes, a racist Japanese caricature depicted as a beetle). The Beetle character was dropped half-way through the series. Gee, I wonder why...
Franklin is rather bad for this, but perhaps the worst example is the character of Moose. An entire story in the first season of the program, based on of the books, was dedicated to introducing this character and his acceptance within the close-knit community. In the episode, he finally joined Franklin's class and became his good buddy, but he was never again seen on the series and no explanation whatsoever was provided for his absence.
Popeye had four nephews introduced around 1940 - as the series went on it was knocked down to three, then two. This was probably due to animation cost restraints, but it comes off as pretty creepy.
Dora the Explorer showed that Diego had an older sister named Daisy. She was replaced with Alicia once he got his show, even though the episode she was in revolved around her birthday.
Lampshaded in an episode of Animaniacs, where Rita and Runt are advertised as "Missing" on a milk carton (the "Rita and Runt" segments having been dropped in the latter half of the series' run, after which the characters themselves put in the occasional cameo appearance, but gradually disappeared - though they continued to feature in the opening credits, and were eventually restored for the direct-to-video movie "Wakko's Wish").
Minerva Mink's disappearance was more justified. Her cartoons were too risque, even by Animaniacs standards — of the two that actually aired, one had a nerdy werewolf who turned into a hunk under the full moon; the other had Minerva using her sex appeal to dispatch a dachshund named Newt — and the executives were afraid she'd be used in a lot of sexually unsavory fan art and fanfiction online. This ended up being a fool's errand, as this became Minerva Mink's fate anyway, thanks to those two episodes. It would have been easier to not have made Minerva a character in the first place.
In the final season of Teen Titans the Brotherhood of Evil recruits nearly every villain that ever appeared in the series. While the appearance of some in the initial lineup is a Snapback from the last time they fought the Titans, some such as the Nufu Source didn't appear in the final battle while Kitten wasn't seen after her encounter with Starfire.
Both of which can be easily explained - Kitten was just a spoiled brat, and Cyborg ATE the Nufu Source. However, some of the villains that the Brain called were actually killed somehow.
Speaking of the Brotherhood of Evil; the Doom Patrol, who were the Brotherhood of Evil's original enemies in the first place, are basically written out after "Homecoming Part 2". What happened after the Titans intervened? The Brotherhood of Evil basically focused on getting rid of the Titans. The Doom Patrol weren't even there to help, nor they were mentioned.
In the first episode, arch-villain Slade is always seen with a silent butler standing at attendance - possibly Wintergreen, Slade's butler in the original Teen Titans comics. He was not used again after this episode.
The H.I.V.E. Academy Headmistress was a bizarre example, as her first (and until the series finale, ONLY) appearance, she seemed to be set up as a Big Bad in charge of training teen supervillains. When the H.I.V.E. organization resurfaced in later seasons, she had been usurped by Brother Blood with no real mention of what happened to her. She returned in the series finale as part of the big final showdown but was quickly dispatched. She later appeared in the comic alongside a new trio of teen villains, but was quickly Bound and Gagged by Robin and presumably arrested. In all of this, it was never explained exactly what had happened that lead to her being booted from her position at the academy.
In The Critic webisodes, ALL the characters from the TV series have disappeared (save Jay Sherman and a brief appearance by Vlada). The worst of all this is that Jay's girlfriend Alice Tompkins is replaced with a Replacement Scrappy named Jennifer.
The Legend of Zelda was based chiefly on the original game in the series, with bits of Zelda II The Adventure Of Link. Despite being a prominent part of the backstory for both games (indeed, she was the reason Link took up his famous quest in the first place), Zelda's nursemaid Impa is not included in the cast. She did, however, feature prominently in the comic book series which launched at approximately the same time.
Also, the Triforce of Courage is never mentioned in the animated series either (the Triforces of Power and Wisdom can count as characters; they even have voices!). As with Impa, Courage is mentioned in the comics and other books (though never seen; it is said to be "in Link's heart") that were otherwise similar to the cartoon.
In American Dragon Jake Long, Rose was separated at birth from both her parents and her twin sister to be raised by the Huntsclan. After the Huntsclan is erased from existence (long story) we catch up with Rose who in the revised timeline lives a normal life with her parents...and no twin sister. Apparently the sister's whereabouts would have been a plot point had the series been given another season.
In the original Teenage Mutant Ninja Turtles cartoon there was an episode involving a female lizard mutant named Mona Lisa. She serves as a potential girlfriend for Raphael and helps him fight off hijackers who were responsible for her mutation (she was originally a human); at the end they say their goodbyes and she secretly follows Raphael and April to the turtle's lair and introduces herself to the rest of them. Despite this being a setup for her being a recurring character and being a fan favorite she is never seen or mentioned again.
That cartoon used to pull the same schtick all the time. They'd have an episode that seemed to set up a new cool character, then they'd usually disappear forever. Remember Metalhead? And Muckman and Joe Eyeball?
Several notable recurring characters, some of which had been on the show from the beginning, just disappeared during the show's 7th and 8th seasons. Season 7 saw the final appearances of the friendly teenage aliens the Neutrinos and the Turtles' young friend Zach. In season 8, Irma, Vernon, Mr. Thompson, and Casey Jones made their last appearances and then vanished without explanation. Bebop and Rocksteady disappeared after season 8, even failing to appear when Shredder and Krang returned for a story arc in the final season with no explanation for the bumbling duo's absence.
On Hurray for Huckle / Busy Town Mysteries, the Hilda Hippo character appears in the opening credits and appears in one or two stories as part of the mystery-solving team, but is absent from all other episodes.
In a couple of episodes of Arthur, George has a slightly younger sister; she last appeared in the Christmas special and so far has not appeared again.
There's also D.W.'s pet toad "Toady Wartface"; after its introduction it made only one other appearance.
Semi-justified because her actress, Billie Lou Watt, died around that time.
The second episode of Nickelodeon's Doug, "Doug Can't Dance", had Roger leading a different group of thugs than usual. These thugs appeared only in that episode.
X-Men: Evolution: After the rise of Apocalypse, Sabretooth just disappears from the show. While its given a small Hand Wave courtosy of Pyro (claiming he was 'playing with a ball of yarn somewhere'), it's more of just Pyro rambling and doesn't mean a thing. Similarly, Destiny disapears in season 3 without any mention. When she last appeared she tells Mystique that she'll be involved in a plot to bring back an ancient mutant, but by Mystique's next appearence, she's working with Mesmero to bring back Apocalypse without any mention or reason.
In the tv series for Barnyard entitled Back at the Barnyard Otis' wife Daisy and their son Ben Jr. are completely absent from the show, Daisy's been replaced by a new female cow named Abby, the strange part is Daisy's best friend Bessie continues to appear on the show.
Why does everyone always forget the donkey from the movie?
Stereo was written out of the second season of Space Goofs.
In Blazing Dragons, Sir Galahot and Sir Hotbreath, two of the Knights of the Square Table, never appeared in Season 2, in which the main focus was on Flicker, Loungelot, Blaze, and Burnevere, but Allfire, Griddle, Flame, and Count Geoffrey and his minions all had some appearances.
DuckTales notably had quite a few recurring characters disappear without any explanation during its second season, including Doofus, three of the Beagle Boys (Bankjob, Babyface, and Bugle), and Donald Duck and Admiral Grimmitz.
Happens frequently in Transformers G1; over time several characters from the 1st and 2nd season stop appearing after the movie and later seasons in order to focus more on the new characters. Having Loads and Loads of Characters and the show being Merchandise-Driven its easy to forget and lose tract on who's who. This meant characters who actually survived, such as Huffer and Sunstreaker, disappeared into thin air and reappeared in the realm of fanfiction forever. The third season was even more confusing to Japanese viewers, because Transformers: The Movie wasn't shown in Japan until later.
Hey Arnold! had a few. Anybody remember Ruth P. McDougal (the sixth-grade girl Arnold had a crush on, though she could have graduated. She wasn't seen much after the Valentine's Day episode where Arnold tries to go on two dates at once and finds that Ruth isn't the dream girl he thought she was, as she was very boring, very shallow, and not very bright) or Mr. Smith?
The first episode with Coach Wittenberg mostly revolved around his son, Tucker, and Arnold helping him get his father's approval. Tucker vanished after that, even though Coach Wittenberg continued to appear, along with the introduction of his (ex-)wife Trish (presumably Tucker's mother?) Tucker didn't even show up when the two remarried.
After the Dexters Laboratory episode, Trick or Treehouse, Mimi and Lee Lee were no longer seen or mentioned (Although they were generally carbon non-white copies of Dee-Dee anyway).
Mandark's sister Lalavava, was never seen or mentioned after her appearance
Come to think of it, after Season 2, whatever came of the Justice Friends Val Halen and The Infraggable Krunk?
Action Hank and The Pony Puffs (Dexter and Dee Dee's heros respectivly) also seemed to have taken their leave after Season 2.
Then there's Douglas P. Mordechai III, Dexter's friend from the schoolbus. He only appeared in three episodes. Justified in that few episodes from Dexter's Lab took place at school.
My Little Pony And Friends had an ever-changing cast, as they tried to market as many ponies as possible. There were some characters that never faded like Wind Whistler or Fizzy but others disappeared without a trace. Notoriously none of the ponies from the first special ever pop up again. You'd think they'd have a close bond to Megan or would at least pop up more, considering they saved the entire kingdom.
I.M. Weasel's sexy nurse, Loulabelle, made her debut in the season 2 premiere, but was not seen or mentioned since the season 3 premiere. It was already implied in one episode that she didn't like Weasel, so that's one reason . The more likely reason was Cartoon Network didn't approve of the dumb blonde stereotype she perpetuated.
Odd since one of the main characters in Ed, Edd n Eddy was one (Nazz), though she doesn't show up as frequently as the other characters.
KaBlam! had a number of these. Sniz and Fondue's room mates, Bill the Lab Guy's daughter Quirky from Action League and Grubby Groo from The Off-Beats (The only adult in that entire short!).
In Rocket Power, the Rocket's neighbors, the Stimpletons, appear a lot less in Season 3, almost to the point of cameos, actually. Also, how often do you see Mackenzie during that season, either?
In Chip 'n Dale Rescue Rangers there was one episode where Dale falls in love with a bat named Foxglove, who loves him back. Chip is also happy because he gets Gadget all to himself. Foxglove was never seen again, though she seems to appear in more Fan Fiction than not.
DisneyAfternoon shows regularly only had a small number of recurring characters while most other characters, even main characters are limited to one episode. These one-shot characters, however, sometimes gained a lot of popularity and fans of their own, sometimes more than some main characters. Chip 'n Dale Rescue Rangers had some more popular one-shots including the squirrel Tammy, the lab rat Sparky, Gadget's Evil Doppelganger Lahwhinie and Gadget's father Geegaw who is only ever seen in a picture. This popularity mostly rose long after the show was produced in a time when there was neither a vocal fandom nor an appropriate means of communicating the popularity of a character to the makers, so none of them ever returned. Both Foxglove and Geegaw eventually returned in the Boom! comics.
In the second season of Jungle Junction, Carla the koala vanished completely.
Alejandro did appear in the first episode of Revenge of the Island still trapped inside the Drama Machine after what happened to him in the finale of World Tour and is confirmed to return to compete in All-Stars, while Blaineley was likely absent due to her almost unanimous hatred in the fandom.
Laura Limpin aka the Big Badolescent from Codename: Kids Next Door made 2 appearances in season 1 and vanished until a cameo in the finale (5 seasons later).
My Little Pony: Friendship is Magic: Twist, Applebloom's best friend in "Call of the Cutie". They have a bit of fallout when Twist gains her cutiemark while Applebloom doesn't (Twist even says "We can still be friends, right?"), and for the rest of the show Applebloom is spending all her time with her new friends, Sweetie Belle and Scootaloo. It really does come across as though Applebloom ditched her closest friend over what essentially amounts to pony puberty.
There's also Derpy. Originally a template meant to be pasted randomly in the background, her eyes were crossed in one episode due to an animation error. She became a fan favorite because of this, so the show's staff started making her a scripted background character in season 2. Halfway through the second season, she actually got a spoken scene and another character even addressed her by name. However, due to her name, her crossed eyes, her low voice (her voice actor thought she was a boy), and her klutzy nature, a group of Moral Guardians decided to interpret this as an attack against mentally disabled people. Because of this, her appearances got less and less common after her episode and she was almost phased out of the show entirely by season 3. However, she has notable appearances during the coronation scene in the season 3 finale, as well as being in the credits for Equestria Girls. Although the creators stated that she would return for season 4.
Averted with Princess Luna. After her release from her Superpowered Evil Side (hinted at Demonic Possession) Nightmare Moon, in the second episode, Celestia says they will rule Equestria together. However, Luna does not appear or is even referenced in any later episodes of Season 1. In Season 2, however, she is mentioned in the two-part premier, and only two episodes later returns in an episode that revolves around her, and has appearances in the finale, and even more appearances in Season 3, so for Season 1 we can say she was Put on a Bus instead.
The DiC seasons of G.I. Joe quietly wrote out the Crimson Twins (Tomax and Xamot), with no word what happened to them after the movie, other than that their business was shut down.
Though most of the characters from the movie made at the very least a cameo in the series once (even Scar did at one point), Nala, the other lionesses, and young Simba (surprisingly) weren't in a single episode of Timon & Pumbaa, though they did return in the sequels.
In Jon Buck's Paradise setting CM is mentioned by the cast of sequel series "Paradise:Veil" and is seen in the story Tall Tales, however his best friend Robert Hallman seemingly vanishes after the 9th "CM and Rob" story.
Many toy-driven franchises that go on for multiple incarnations would often find many characters dropped from later series. The most notable case is G.I. Joe's Zarana: Mostly seen as an attempt to add a second female to Cobra, but she never made a screen appearance since the DiC-produced episodes. While she DID receive an expanded role in the DDP Joe comics, she is the only 1982-94-originated female character to never even get a mention in any of IDW's new Joe comics! Even Cover Girl and Pythona get odd appearances every now and then! She doesn't appear in the Larry Hama-penned IDW continuation of G.I.Joe: A Real American Hero AT ALL!