Chip 'n Dale Rescue Rangers has plenty of one-episode wonders. Foxglove, the bat from "Good Times, Bat Times", appeared in only this one episode, but she seems to be part of a Fan Fic cast more often than not, she might have more fans than Monterey Jack, and she has even got a website dedicated to her. Tammy, the squirrelmaid from "Adventures in Squirrelsitting", comes in second. There are several more, including the lab rat Sparky from "Does Pavlov Ring a Bell", Gadget's Evil Twin Lahwhinie from "Gadget Goes Hawaiian", and Geegaw Hackwrench (who never even appeared on-screen, apart from a portrait in "To the Rescue" part 3). Unlike the others, Foxglove has gone on to make regular appearances in the 2010 CDRR comic series produced by Boom! Kids.
Speaking of Chip and Dale, there was one short named "Two Chips and a Miss", in which a character named Clarice fills in the role of Chip and Dale's girlfriend. This was her only appearance, and yet she has a HUGE popularity (even appearing in Disney Parks for some reason), especially in Japan. Who knew that a one appearance character would cause THIS much popularity?
Hank Scorpio only appeared in one episode, but is a truly memorable James Bond villain parody who is also an excellent example of an Affably Evil character. Such was his popularity that he was initially considered to be the main villain for The Movie. The plan was canned as the writers didn't want to use a villain from an episode over a decade old. His voice actor (the ever awesome Al Brooks) was kept to voice the final villain, who still shares many quirks worthy of Scorpio.
Frank Grimes was only in one episode too — he died. But he's been mentioned many times since, with a Running Gag where Homer forgets that he's dead, and his son (Frank Grimes, Jr.) is a villain in "The Great Louse Detective".
The twitchy Gun Nut from the episode where Marge joins the Springfield Police.
Chief Wiggum: All right, you scrawny beanpoles: becoming a cop is not something that happens overnight. It takes one solid weekend of training to get that badge.
Gun Nut: Forget about the badge! When do we get the freakin' GUNS?!
Chief Wiggum: Hey, I told you, you don't get your gun until you tell me your name.
Gun Nut: I've had it up to HERE with your "RULES"! [walks off]
The Very Tall Man, the only original character introduced in "22 Short Films About Springfield" ) who was a caricature of writer Ian Maxtone-Graham, who was also rather tall), who left a rather big impact on it by punishing Nelson for mocking him. His only other appearances have been cameos.
Dr. Colossus, the boastful - but easily humbled - Mad Scientist from the second part of "Who Shot Mr. Burns?" His two rather brief scenes were so impressive, he is the Trope Namer for Cartoonish Supervillainy. (Unfortunately, those scenes were cut for syndication, making them hard to see these days.)
The inhabitants of the Neutral Planet appear in only one episode of Futurama, but their "neutral humor" was a particular favorite of the fans and producer David X. Cohen.
Neutral President: If I don't survive, tell my wife "Hello."
"That Guy" (The 80s Guy) only appears in the episode "Future Stock", but is still revered for his 80s style.
That Guy: There are two kinds of people: sheep and sharks. Anyone who is a sheep is fired. Who is a sheep?
Dr. Zoidberg: Errr, excuse me... which is the one people like to hug?
That Guy: Gutsy question. You're a shark. Sharks are winners, and they don't look back because they have no necks. Necks are for sheep.
Jonathan Frakes (or rather his bottled head) appears in the Star Trek parody/homage episode just long enough for one line. And yes, it really is Frakes' voice. That's dedication for you.
This also applies to other one-episode-wonders from Looney Tunes, such as Pete Puma and Count Bloodcount ("Hocus pocus!" "Abracadbra!"). Many fans are actually surprised to realize they only appeared in one cartoon. Multiple decades of television reruns probably helps.
Back Alley Oproar is quite funny with Sylvester keeping Elmer up with his singing, then this guy comes along and steals the show.
From The Powerpuff Girls, two words: Rowdyruff Boys. From ONE episode came a raging torrent of fanfics, raging internet debates, and impassioned pleas to Craig McCracken to bring them back, nearly all of them completely missing the point of what the Boys were about. (What they were about: Fight, fight, fight, gross out, fight some more. The Mayor had more depth than that.) And when McCracken finally gave in and brought them back, they hardly changed at all! To this day they're some of the most popular PPG supporting characters EVER (even have a dot-net website), despite being essentially just a more powerful and vicious Gang Green Gang.
Dick Hardly, a one-shot villain who made literal rip-offs of the girls to sell to cities all over the place, managed to be this. Likely due to being probably one of the worst villains in the show (possibly even worse than Him, who is supposedly the devil himself), which makes him rather easy to remember. Another thing making him stand out is he's the only human in the series to actually be Killed Off for Real.
In the three seasons of Avatar: The Last Airbender, we see Koh the Face-Stealer twice. One episode, in the first season, when Aang first travels to the Spirit World, and another time in a flashback during the finale, which reveals a previous Avatar's experience with him. Why do we remember him? Because he's a gigantic centipede trickster spirit who will steal your face and wear it like a mask if you show the slightest twitch of expression.He doesn't kill you. Look at the monkey outside his lair for proof. And technically, he's not even a bad guy. Few monsters have ever been so imaginatively, effortlessly terrifying - it's no wonder fans clamoured for more.
Let us not forget the Foaming Mouth Guy. He has threenicknames, the aforementioned Foamy Mouth Guy, just Foamy, and Frothers.
The cabbage guy is just referred to as... the Cabbage Merchant. He was so wildly popular that in the Sequel SeriesThe Legend of Korra, he (or rather, his descendant) was brought back as the owner of a now big successful Cabbage Corporation. He even gets to say a variation on the famous line - "Not my Cabbage Corp.!"
Fanficcer favorite Song, who appeared exactly once (in "The Cave of Two Lovers"). Her chemistry with Zuko was such that she's pretty much option #3 for Zuko shippingnote Hetero shipping, anyway... (behind Katara and Mai).
Jin from the Breather Episode "Tales of Ba Sing Se" is reasonable popular for similar reasons as Song.
Any time the Gaang (a.k.a the original Team Avatar) show up in flashbacks, or whenever we see an elderly Katara. Sokka in particular who has only one line. There's also adult Aang's appearance as a spirit in the first season finale.
Howl aka Hot Order of the White Lotus guard who only appears ten seconds in the first episode but it was enough for fans to ship him with Korra.
Fire Lord Izumi is shockingly popular within the fandom for a character who appears in two scenes and only has about three lines. This is probably largely because she is the daughter of a beloved character from the original series and because the fandom knew about her existence three seasons before she appeared onscreen. Also probably working in her favor is the fact that in the only scene where she speaks, she goes head to head with an extremely unpopular character and quickly establishes herself as a very competent leader. Her popularity is such that she was being shipped with multiple characters before her name was even revealed.
As of this writing, exactly one episode of The Legend of Calamity Jane is available for viewing on YouTube. And while he would have gone on to be a regular character, until somebody finds a way to release the rest of the series, Clancy Brown's two-minute appearance as Wild Bill Hickok just may be the best thing about it.
Ariel, Niko's mentor was such a colorful Badass Grandma that she's a favorite for Galaxy Rangers fanfic writers, despite showing up in only one episode.
Invader Zim had Tak, a scary and Crazy Awesome psychopathic female counterpart to Zim. She only appeared in one episode, but she's hugely popular. (Actually, the creators had planned to bring her back regularly and feature her as a major antagonist, but then...well...the show got cancelled before that could happen.)
The Hobo in "Gaz, Taster of Pork."
He would've gotten a co-starring role in a whole episode, if the series continued much further.
Freakazette of Freakazoid!, at least according to CR of YouTube and That Guy with the Glasses (as seen here). She only appears in about four seconds of an introductory song, but never in the show. CR rags on the creators for never doing anything with the character after putting her in a spotlight on top of giant letters spelling her name. Yeah, Viewers Are Morons for thinking that she'd actually be in the show, right? note She was going to appear in a later episode of the series titled "Enter Freakazette!", but it was cancelled before that could happen (thus leaving the script unproduced)
Candlejack starred in one episode and appeared briefly in only two others, yet somehow he became popular and memetic enough to get his own page on this very Wiki.
They also made their appearance in the 1987 series episode, "Dirk Savage: Mutant Hunter".
The old The Tick animated series featured, in its run, precisely one episode with a would-be villain calling himself 'The Evil Midnight Bomber What Bombs At Midnight' (yeah, baby!). This character was so blisteringly off-the-wall - even by The Tick's standards - that he is easily one of the most memorable characters in the entire series.
"And so he says to me, you want to be a bad guy? and I say Yeah Baby! I want to be bad! I says Churchill space ponies I'm making gravy without the lumps! Ah ha ha ha ha haaaaa!!!!!"
TEMBWBAT got a later one-scene appearance trying to get into the villain awards but being rejected by the bouncer.
"One of these days, baby! MILKSHAKE! BOOM!"
After Remy Buxaplenty's lone appearance on The Fairly Oddparents ("Fairy Fairy Quite Contrary") many fans clamored for another appearance from him and his fairy, and the clamors grew especially after a Halloween episode which had an appearance by Remy's father (but not Remy himself). He eventually got a couple more episodes a few seasons later.
Originally, the Metalocalypse character Dr. Rockzo the Rock n Roll Clown (he does cocaine) was a minor character at Murderface's birthday party who only got 50 seconds of screen time. However, the fans and creators liked him so much, he was added as a recurring guest star in 5 more episodes.
In that first 50 seconds, he says he does cocaine three and a half times.
Squilvia appeared for only one episode, and she subsequently gained a number of fans.
Transformers Generation 1 has a ton of these due to Loads and Loads of Charactersneeding to be sold and not loads and loads of time. Some characters make very memorable appearances that are sadly rare and brief. Sixshot, for example, is introduced by Galvatron as a 'one-robot army,' proves it by taking out the entire Aerialbot team singlehandedly, earning his name by using each of his then-unprecedented six transformations to do it, and is then not seen again.
Can also go for accessories. At one point in the three-part premiere, Optimus and Megatron are fighting on top of a dam. Optimus transforms his arm into a glowing energy ax. Megatron transforms his into a glowing energy morningstar. They battle for a minute or two, before Megatron leaves by spinning his morningstar in the air and flying off as if it's a helicopter propellor. These weapons are never seen again. You'd think it'd be a Big Lipped Alligator Moment, but it's so hugely memorable that there have been homages to it ever since, popping up in toys and comics often. It's almost certainly the reason Transformers Animated Optimus has an axe as his main weapon.
Fred from Courage the Cowardly Dog. Despite only appearing in one episode (apart from a brief cameo at the end of "Ball Of Revenge") he has become one of the series' most recognizable and frightening villains.
The blue nightmare creature from "Perfect." Although it only appeared in a ten-second nightmare scene during the final episode and barely spoke, it has become known as one of the series' most frightening characters.
Kitty and Bunny from the episode "The Mask," for having personalities, backstories, and relationships that displayed surprisingly mature themes.
King Ramses. Despite only appearing sporadically in a single episode, with no future cameos, he has become one of the series' most famously frightening and memorable characters. His creepy and highly repeatable phrases certainly help his memorability.
Teen Titans: Argent. Oh so much. A Pettanko dressed in the whole gothic dress thing and has an Australian accent? And her big action during the scene was...getting a communicator from Starfire. Yeah. Her minimal time on screen didn't stop her from becoming a fan art favorite.
The Modifyers has Baron Vain, whose psychopathy and ridiculousness won the hearts of those who actually saw it.
TaleSpin has many one-shot guest star characters who are popular with the fans.
In episode 14 of My Little Pony: Friendship Is Magic, titled "Suited For Success", a white unicorn with a blue-and-turquoise mane appears on screen for about 6 seconds. Judging from the turntable in front of her, fans decided that she is a DJ. She got a name (Vinyl Scratch), a stage name (DJ P0N-3), and a few fanfics and quite a lot of fanart, and shout outs in commercials and an official t-shirt. And now she's toy.
Said DJ pony makes a return in the Season 2 finale for yet another One-Scene Wonder, and became a major background character in the Equestria Girls movies.
Then there are the Shadowbolts, who have gotten quite a few fans despite them not really existing - including Rainbow Dash, who dresses up as one for Nightmare Night.
The fandom loves these. Octavia (the cello-playing pony from "The Best Night Ever"), Sapphire Shores (a pony pop-star who kicks off the plot of "A Dog and Pony Show"), the camp sea serpent from "Elements of Harmony" (who has gained the nickname "Steven Magnet" thanks to the hilarious youtube closed captions) and Princess Luna (who returned in Season 2, episode 4 and later became an Ascended Extra) and countless other characters get no more than a minute of screen time and a few lines of dialogue (if any), yet own their screen time so hard people are still talking about them.
Crackle the dragon. A 4 second Cutaway Gag of a very odd looking dragon that just happens to look like Twilight's Rainbow's and Rarity's Paper-Thin Disguise.
The episode "Hurricane Fluttershy" gave fans quite a couple One-Scene Wonder pegasi: A pair of grayish white maned pegasi with unique hairstyles named Flitter and Cloudchaser (the latter of which can also be seen in a season 3 trailer), a darkened stallion named Thunderlane, a white-coated pegasus with a green and pink mane named Blossomforth, and a beefed up muscular pony who notably screams YEAH! a handful of times in the episode. Each appears only briefly and have a handful of lines at most, but true to form they've each developed some pretty big fan followings. Most of them have since become minor recurring characters in the show.
In "Games Ponies Play" there was a flashback scene where Rainbow Dash is with a stallion with a rainbow mane just like her. Fans are calling him Rainbow Dad, with a decent fan following from it. He is officially named Rainbow Blaze in merchandise.
In the Season Four opener, Discord gave Twilight a scepter with a goofy face to mock her princessiness. As happened with Derpy, the Twilicane has exploded across the fandom. It took one day for someone to make a 3D model of it, someone else to set up a Tumblr, and for someone else to do this.
Firefly, Medley, Twilight, Applejack, Bowtie, Scorpan, and Tirek are some of the most popular My Little Pony characters but in American canon only appeared in the first of the two My Little Pony TV Specials.
Junebug, the sherbet orange-maned mare with flowers in her saddlebags, has only appeared in two episodes to date, and her sole speaking role is in "Secret of My Excess" when Spike demands a birthday present from her.
Sunny Rays appeared for but a few seconds moving clouds at the beginning of "Look Before You Sleep", and did not appear again until late in Season 4. Despite this, she has recieved a brushable toy in the Wedding Invitation line.
The Ed, Edd 'n' EddyGrand FinaleMovie introduces us to Eddy's long-unseen older brother. He only gets 5 minutes of screen time and yet leaves a huge impact as a genuinely dangerous person who beats his younger brother and Edd for fun.
In The Critic, Orson Welles appeared in two minutes total over two episodes, and has spawned more memes than any other character on the show.
"They're even better when you're dead!"
Family Guy has Ernie the Giant Chicken, a rival of Peter's who has appeared in four episodes (although he's also made a few minor cameos in some of the other ones) where he'll show up and start slugging it out with Peter for several minutes in a series of over the top brawls that just escalates in insanity with each new fight. It doesn't matter what else will happen in the episode; the second Ernie shows up that's going to be the one thing everyone remembers about it.
Jeffrey Fecalman, the antagonist of the only particularly serious episode of the series. Only appeared in that episode and one earlier one, and he's significant because nothing he does is played for laughs. The whole point of his appearance is to drop an anvil about domestic abuse.
While chock-full of memorable one-shot characters, episode 50 of Samurai Jack took it a step further when it gave us X9, a highly-skilled robot assassin with a Film Noir vibe and mobster zoot suit who was the last of his kind, due to receiving an emotion chip that gave him a sense of self-preservation when the other bots let themselves get blown to bits. Unlike his brethren, X9 grew to hate the senseless acts of killing and disappeared from Aku's watchful eyes, then found new purpose in life when he befriended a dog named Lulu... sweet thing. Although X9 appears once, he's the only character with a speaking line that episode, and he's not a Filler Villain with generic motives, but a complex character with a valid reason to take up his gun. More importantly, we're treated to a deep, heartwrenchingBack Story, which makes him that more endearing to the fans and viewers watching- especially when Aku kidnaps Lulu and blackmails X9 into coming out of retirement to kill Samurai Jack. The rest of the episode after the How We Got Here segment amounts into a tension-filled showdown between Jack and X9- one of the few times you actually don't want to see Jack's enemy cut down... which makes the ending of the episode all the painfultowatch. Made even worse knowing the show didn't last long enough to show if Jack ever rescued Lulu... sweet thing.
The (possible) future Warden on Superjail!, who was the reason why the Time Police arrested the Warden despite him not (yet) committing any crimes in the first season finale. He got maybe three minutes of screen time, and was loved for being an Axe CrazyFuture Badass who conquered the world.
The doberman puppy from "Superfail" in season 3 wound up with a lot of fanworks dedicated to him, owing to the twisted Tear Jerker nature of the flashback that he appeared in.
Adventure Time could claim a verifiable treasure trove of these, between one or two-line characters like the Tiny Manticore in "Son of Mars" or the Old Man Prisoner from "Gut Grinder" or single-episode characters like Lorraine from "BMO Noire" or Wormo from "Apple Thief." Of course, many of these characters go on to become an Ascended Extra.