Many older kids shows, like You Can't Do That on Television and Kids Incorporated, substituted the entire cast, and Kids Incorporated did so repeatedly. Their reasoning is likely similar to why the Vienna Boys' Choir and Menudo boot their kids out at 13.
Season 7 introduces Janis Gold, a frumpy bespectacled computer technician, who is the FBI's version of Chloe. They bring Chloe back for a few episodes, and they don't get along.
The character of Mandy is another example. If the producers couldn't get Mia Kirshner, the actress who played her, they created another sexy terrorist. Season 4's Nicole is a prime example because she behaves in EXACTLY the same way as Mandy would, she has sex with a character to get him on side, then reveals her true colors. Mandy did more or less the same thing in the first episode. Which is amusing in itself considering Mandy actually did return at the very end of the fourth season.
Olivia Taylor's only real existence on the show was to essentially play Sherri Palmer to her mother Allison's David: The former is a corrupt, manipulative bitch family member to the latter who is the President and very much a strong moral force for the country.
Since the MCUcouldn't use any X-Men characters or the term "mutant" at the time the show was airing, the writers used the generic term "Gifted" to describe people with superhuman abilities. This became significantly more pronounced when The Inhumans were introduced in the second season, with many viewers and critics noticing that their storylines seemed suspiciously similar to stuff from the X-Men mythos. These included plots about increasing public fear and paranoia regarding the Inhumans, Inhumans being forced to register with the government, and even some of the heroes becoming divided over a controversial "cure" for Inhuman powers, all of which had been done before in various X-Men media. Hive was even given a new backstory and set of motivations that made him very similar to Apocalypse, one of the X-Men's recurring Big Bads.
Agent Antoine Triplett, who joins Coulson's team as a Sixth Ranger right around the time that Grant Ward is revealed to be a HYDRA agent. Both Ward and Triplett are badass, manly agents (compared to the meek Fitz and Team Dad Coulson) who previously trained under John Garrett and serve as potential Romantic False Leads for Fitz-Simmons.
Averted with Sarge. While he looks identical to Coulson ( who was killed off at the end of Season 5) and is even played by the same actor, the two characters are nothing alike.
Besides The Other Darrin, Roger Davis, Alias Smith and Jones replaced the character Clementine "Clem" Hale with Georgette "George" Sinclair. Probably a case of the writers recycling scripts already written for the other character.
When Nickelodeon's variety show All That began, Katrina Johnson was easily the youngest-looking cast member and was mostly used to play a variety of little girl characters. In Season 3, with Katrina looking too old to pull off these roles, Amanda Bynes was added to the cast to fill the void. Katrina left the show entirely later in that season.
Inverted on All in the Family: The character of George Jefferson was expressly written for Sherman Hemsley, who was unavailable at the time the show's early seasons were shot due to his appearance in a Broadway musical; the character of George's brother, Henry Jefferson, was devised as a placeholder until Helmsley became available in Season 4 (although George was "on" the show as an offscreen character in the earlier seasons).
The German soap opera Alles Was Zahlt originally dealt with Diana Sommer, who was a plucky blonde delivery girl turned up-and-coming figure skater. In the first episode, Diana was sort of hit by a car... which led to the Meet Cute introduction to her boyfriend Julian. After Julian died and the actress playing Diana decided to leave the show, a new character was introduced: the plucky blonde circus performer turn up-and-coming figure skater, Stella. Upon arriving in town her car broke down, which meant she almost got rear-ended by her immediate love interest, Lars. It wouldn't be so bad if Stella and Lars were bearable, but unfortunately, they're not.
Done on 'Allo 'Allo! when Mimi and Captain Bertorelli appeared as substitutes for Maria and the German Captain Hans respectively — in particular, Mimi was at least as short as Maria and both had fiery tempers. It allowed them to continue the gag of Mimi/Maria having to get a stool to stand on in order to hug René. Later, Monsieur Leclerc was replaced by his twin brother after the original actor died. Captain Bertorelli and the second Leclerc were then replaced in a The Other Darrin manner. In the final season, the actor playing "Herr Flick of the Gestapo" was replaced - this was explained as him having plastic surgery to prepare for Germany losing the war. Also parodied in the series, when René's death was faked and he was forced to pose as his own Suspiciously Similar Substitute twin brother for the rest of the show.
The character of Tyr, a Nietzschean who could not be trusted was replaced by Rhade, a Nietzchean who could not be trusted. Tyr went on to become a complete wuss when the actor guest-starred in later episodes.
The character of Doyle in the final season is also somewhat of a replacement for Lexa Doig's Andromeda when her role needed to be reduced due to the actress' pregnancy. Doyle provided a love target and protector for Harper, among other regular Rommie duties.
When Gomer Pyle left the series in 1964 for his own spin-off, Gomer Pyle, U.S.M.C. (of "'PYYYYLE!'...'Shazam!'" fame), he was replaced by equally hayseed cousin Goober Pyle. Goober had originally been introduced as Goober Beasley, and had been frequently referenced by Gomer; the two appeared together in precisely one episode as cousins. Once Gomer left the show, Goober Beasley became Goober Pyle and took over Gomer's job at the filling station and overall role in the series.
New deputy Warren Ferguson, though he had his own distinct verbal tics, was very, very similar in terms of attitude and (barely marginal) competence to departed deputy Barney Fife. Unpopular with the fanbase, Warren was quickly Chuck Cunninghamed out of the show.
Andy's steady girlfriend in the first season was pharmacist Ellie Walker; after she was written out of the show (apparently due to lack of chemistry between Andy Griffith and Elinor Donahue), Andy was given a couple of more temporary love interests (both nurses) before schoolteacher Helen Crump was finally introduced in season 3. All of Andy's girlfriends are somewhat similar, being smart working women with an independent attitude (for the era). Helen's strong jealous streak was perhaps more pronounced than in the others.
When the show was retooled as Mayberry R.F.D., Sam Jones and his son Mike essentially became the substitutes for Andy and Opie Taylor.
Mr. Harmon, Old Mr. Grace, and Mr. Spooner replacing Mr. Mash, Young Mr. Grace, and Mr. Lucas respectively.
Also Mr. Grainger, the head of menswear, was replaced by Tebbs, Goldberg, Klein, and Grossman before they eliminated role and made Mr. Humphries head of the department.
When Mr. Lucas was replaced by Mr. Spooner. Mike Berry, who played Mr. Spooner, said that his first few scripts had "Lucas" crossed out and replaced by "Spooner" in pencil.
After Ian Hendry quit his leading role as Dr. David Keel on The Avengers after one season, the producers were left with a number of leftover scripts. Rather than retool them, a new character named Dr. Martin King was created for several of them, while others simply had the name "David Keel" crossed out and "Cathy Gale" pencilled in, creating a rare gender-swap substitute and setting Cathy up to become iconic.
Babylon 5: Straczynski has stated that every major character on the show had an "escape hatch" for each season, to allow the actor to be replaced if necessary without affecting the overall story arc. While some new characters fill the same position but are unique characters, others are very similar to the character they replaced:
Susan Ivanova and Elizabeth Lochley, however, are the same cynical XO with a messy personal history. The difference between the two changes and their effect on the show is marked, as was general reaction.
Ivanova was herself a Suspiciously Similar Substitute for Laurel Takashima from the Pilot MovieBabylon 5: The Gathering. According to JMS, that wasn't the original intention. The two characters were originally supposed to coexist until the end of the second season when Laurel would turn out to be The Mole and leave the show (written in because JMS knew Tamlyn Tomita wouldn't want to commit to five years) and Ivanova would become the executive officer... but then Tamlyn Tomita decided not to come back for the series at all.
Talia Winters replaced Lyta Alexander when the series began; in a recursive twist, though, when Andrea Thompson decided to leave the show, they brought back Lyta in a double-un-Suspiciously Similar Substitute maneuver.
Stephen Franklin replaced Benjamin Kyle.
Marcus the unlucky in love long-haired pompous English-sounding character who quoted Shakespeare replaced in Season 5 by Byron the unlucky in love long-haired pompous English-sounding character who quoted Shakespeare.
Babylon 5 did this with alien species too. After the Shadows left the galaxy, a suspiciously similar race called the Drakh appeared, handwaved as the "dark servants" of the Shadows.
The final season of Ballykissangel introduced the elderly farmer and pub regular Louis Dargan (Mick Lally) after the death of Birdy Sweeney, who played elderly farmer and pub regular Eamon Byrne. Unlike Eamon, however, Louis was never important to the plot and never spoke an intelligible sentence.
Battlestar Galactica replaced Billy Keikeya with Tory Foster. This is actually the only Battlestar example. Given the improvisational nature of the series' writing, it's unclear if Billy would have followed a similar arc to Tory, had Paul Campbell remained on the show.
According to Word of God, Matt and Summer were created to replace Eddie and Shauni after their respective actors left the show at the beginning of Season 3. The writers weren't very subtle about this, even having Matt move into Eddie's old houseboat at one point.
Season 5 introduced cocky Australian lifeguard Logan, who was basically a replacement for cocky Australian lifeguard Trevor from Season 1.
Summer's initial love interest was Jimmy Slade, a blonde surfer who lived out his car, had an abusive dad and dreamed of going pro. During a period where Jimmy had been Put on a Bus, Summer got a one-episode Replacement Goldfish named Steve Thorn, a blonde kickboxer who lived out of his car, had an abusive dad, and dreamed of going pro.
Beakman's World substituted its lovely young female assistant not once, but twice. Both were a result of the show's fate: The first switch happened as the show moved to CBS from syndication (and Alanna Ubach deciding to do movies instead), and the second happened after an Un-cancellation (and Eliza Schneider deciding to do stage shows instead).
Mitchell, a reformed vampire with a troubled past who's sworn off blood and lives alongside a werewolf and a ghost, was killed off at the end of Series 3. Series 4 replaces him with Hal... a reformed vampire with a troubled past who's sworn off blood and lives alongside a werewolf and a ghost.
At the same time, George, the resident werewolf, also left. His role in the house was replaced by another werewolf who had almost nothing in common with George. The reason? Tom, his replacement, had been a recurring character since the start of the third series. Zero new characterization was required.
Tiffani Thiessen's Valerie Malone on Beverly Hills, 90210. Valerie was introduced after Shannen Doherty was fired from the show and was a brunette of similar temperament to Doherty's Brenda who lived in her room and slept with her ex-boyfriend. Her twist was that she was a pot-smoking 'naughty girl', as the characters in the show would constantly remind us.
To an extent, Hugh Laurie in the third and fourth series of Blackadder seems to have filled this role (aristocratic fop) in replacement of Tim McInnerny from the first two series, after McInnerny left because he didn't want to be typecast. When McInnerny rejoined the regular cast in the fourth series, his character resembled that played by Stephen Fry (brown-nosing rival) in the second series, with Fry in turn now playing a character more akin to that of BRIAN BLESSED and Miranda Richardson respectively (insane tyrant) in the first two series. This slightly convoluted game of "musical chairs" in regards to actors and characters appears however to have been of little detriment to the series.
In Blake's 7, substitutes are always the same gender as the outgoing character, for no particular reason but to make up the numbers. Jenna is replaced by Dayna, Blake is replaced by Tarrant, and Cally is replaced by Soolin. Slightly subverted in "Rescue", though, where the tough guy and the female pilot are replaced by a male pilot and a tough chick, respectively.
In Blue Bloods Danny Reagan's partner Jackie Curatola left the series a third of the way into season three due to actress Jennifer Esposito's illness. Danny had two partners that each lasted about five episodes each before finally ending up with Maria Baez as Jackie's permanent replacement. Both characters are Latina detectives from rough backgrounds, and with similar temperaments.
Jeffrey Coho from Boston Legal is an interesting example, in that he was the substitute for a character who was still on the show. Over the first two seasons, the main character Alan Shore transformed from being a rather-slimy-lawyer-with-a-deeply-buried-heart-of-gold type to a civil rights crusader. Jeffrey Coho was brought onto the show at the beginning of Season 3, and was identical in personality to Season 1 Alan, even down to his politics and his feuding with Brad Chase (except, mercifully, for the friendship with Denny Crane, which was only ever Alan's).
Although not as obvious as some other examples, the producers wrestled with who they could get to replace Cordelia's snarky truth-telling character (who had left for Angel, where she'd undergo a whack of Character Development and change personalities anyway). At first, when getting wind of the popularity of Spike and deciding to keep him on, they'd thought to have him do it, but they later decided to use Anya, a previously one-episode appearance, to become a regular and take over Cordelia's role in the group.
Spike, the Vampire-fighting-for-good, is curiously similar to Angel. Eventually even the slightly-different motivation, the behavior-dampening hardware placed in his brain, is written out and he is given a soul just like his counterpart. And yeah, they both date Buffy. Their personalities are not remotely similar, though. The Scoobies occasionally seem to forget which of the two vampires they are dealing with, trusting Spike with information and roles appropriate to Angel, while he casually betrays them and frustratedly reminds them that he's 'evil, remember?'
Spike: Okay, I think I know what to do. I'm gonna find this girl Faith...and tell her exactly where to find each and every one of you. (Cue shocked expressions from Xander and Giles. Spike sighs.) Will at least one of you bloody Scoobies try to remember that I hate you all! Just because I can't do the damage myself doesn't stop me from pointing a few loose cannons your way."
The trope was inverted with Kennedy, who was deliberately made very different from Willow's previous love interest Tara. Perhaps not the best idea, as Kennedy was pushy, arrogant, and abrasive where Tara was shy, gentle, and empathetic. She was not received well.
Last seen as a paramilitary homosexual Slayer leader figure, fans hated Kennedy No. Matter. What. It didn't matter what changes were made. So the character of Lake Stevens was made up, a paramilitary homosexual Slayer ally leader figure who has much of the traits the writers wanted from Kennedy, but better. Fan reaction thus far has been to wait and see what her intentions for Willow are.
There's a textbook subversion in season 1, after Angel loses Doyle. He complains that his link to the Powers That Be is gone, only to be told that "whenever a door closes, another opens." Enter a very Doyle-like character...who turns out, after a series of misdirections, to be the Monster of the Week, not the new sidekick. Cordelia gains Doyle's powers and role.
Doyle himself was a Suspiciously Similar Substitute for Whistler, a character who appeared briefly in flashbacks in Buffy's second season finale and recruited Angel to the side of good. Both are sarcastic demons (half-demon, in Doyle's case) who work for the Powers That Be. Doyle was originally intended to be Whistler, but the actor was unavailable when the show was greenlit, so they reworked him as newcomer Doyle. In "City of" Doyle even wears a hat similar to Whistler's iconic hat.
Joss Whedon admits that after Cordelia went insane, fell into a coma, and was absent in the show's final season, the writers felt that the show had lost an important puzzle piece. Enter Harmony. Dim-witted, blonde, and completely peculiar vampire who seems to carry the personality of Cordelia circa Season 1. They even went as far as adding her as a main character in the opening credits for the final six episodes. Though since Harmony had been there since the very first episode of Buffy (and being one of the Cordettes) her character was already known and accepted. Word of God is that Harmony was supposed to be a recurring character once she arrived on Angel...but they forgot about her until the final season. Then, they ended up having her in every episode, so it was somewhat necessary to make her part of the main cast.
For Season Five, Eve served the part of Cordelia that was to play Angel's foil. Spike as in Buffy Season Four came on to give the much-needed sarcastic remarks. Illyria, later, became the one who provided conflict by always saying it like it is.
Eve also effectively replaced Lilah Morgan as the untrustworthy senior female at Wolfram & Hart, as she herself commented on in her first scene.
Charlie's Angels. At the end of Season 1 Farrah Fawcett left the series and her character, Jill Munroe was replaced by her kid sister Kris. The show's ratings soared after that.
Averted: Rebecca Howe (a ruthless and hot corporate exec, who transmogrified over the years into an almost total wreck) was very distinct from her predecessor Diane Chambers (a bookish and pretty in a girl-next-door-way barmaid, whose main fault was her tendency to over-intellectualize everything).
Semi-averted: The sweet-natured, dimwitted old bartender Coach was replaced by the sweet-natured, dimwitted young bartender Woody Boyd. Though similar in some ways, Woody's wide-eyed-young-rube-in-the-big-city vibe is markedly different from Coach's lovable-old-guy-who-took-too-many-baseballs-to-the-head vibe.
Lampshaded: Al, the elderly man who sat at the opposite corner of the bar from Norm and occasionally made sarcastic comments, was gradually replaced by Phil, the elderly man who sat at the opposite corner of the bar from Norm and occasionally made sarcastic comments. In the Reunion Show episode of Frasier, Frasier says how good it is to see Al again, only to be told "I'm Phil, you jackass! Al died!"
Agent Shaw on Chuck seems pretty similar to Bryce from Seasons 1 and 2. They're both romantic rivals to the lead character, they both mentor him on how to be a spy, and they both are super spies.
Citizen Khan's first series had a red-headed mosque manager named Dave who converted to Islam later in life. In Series 2, he's replaced by a red-headed mosque manager named Dave who converted to Islam later in life. These are distinct characters, not an example of The Other Darrin. One suspects that the writers had Series 2 almost completed when Kris Marshall decided to leave and only added a few lines introducing Matthew Cottle's version of Dave into Series 2 first episode to avoid having to go back and make more extensive changes.
The third season introduced an annoying gang of German foosball players led by a man named Juergen. When the group reappeared in Season 4, Juergen was replaced by his previously-unseen brother Reinhold, presumably because the creators couldn't get Nick Kroll to reprise his role.
After Pierce's actor Chevy Chase left the show, the writers introduced Professor Buzz Hickey, a Grumpy Old Man who has been at Greendale for a much longer time than the rest of the group, a Jerk with a Heart of Gold, a bit of an outsider and sort of a mentor to Jeff. He even takes Pierce's seat at the study room table.
Then, when Jonathan Banks left the show due to commitments to Better Call Saul, Buzz was replaced with Elroy Patashnik, anotherGrumpy Old Man, this time played by Keith David. Despite some major differences (Elroy was a genius, black and not a prior Greendale student), it was clear the writers were using him to fill the same basic role. As Elroy joined the cast after both Donald Glover and Yvette Nicole Brown had left the series as well, he also had to step in for Troy and Shirley as the group's new token black member. All this was actually lampshaded at one point:
Chang: Is he black Pierce? Old Troy? Or Shirley without a giant purse?
Phil in Corner Gas replacing Paul as the Cree with long hair and the four-letter name that starts with P and ends with L who works as the head bartender. The only difference apart from name is that Phil looks older and has a deeper, less enthusiastic voice.
Emily Prentiss and David Rossi were replacements for Elle Greenaway and Jason Gideon respectively. Both characters were initially hated by many fans, but gained pretty good fanbases the longer they remained on the show.
The trope is played straight with Prentiss, but not Rossi. Word of God from creator Ed Bernero on the "About Face" commentary says they wanted to make him as least like Gideon as possible, so they made him an egotistical wannabe rock star of a profiler who doesn't really "do" teams, and the first thing he does is shoot a bird. Jason Gideon was part ornithologist and part birdwatcher. Many times throughout Mandy Patinkin's run you would hear and see references to his character's love for birds. A Take That! indeed!
After JJ's departure, another new character joined the team—meet Ashley Seaver, FBI cadet and based on previews, the daughter of a serial killer. Yes, she does look like JJ superficially, but the majority of the fanbase disliked Seaver prompting the return of JJ (and Prentiss who left at the end of last season).
Tough, dark-haired multilingual Elle Greenaway leaves after season 2, to be replaced with tough, dark-haired, multilingual Emily Prentiss. Emily Prentiss leaves the team at the end of season 7 and is replaced in season 8 with tough, dark-haired, at-least-bilingual (knows ASL) Alex Blake. There seems to be a trend here...
The show replaced two characters in the ninth season, with Ray Langston, and Riley Adams, though they seem to be the latter type, each having their own character traits.
DB Russell is said to be a straighter version of this, because he has some similarities to Grissom, though not so close that it screams "Grissom Light".
By comparison, CSI: NY replaced Aiden Burn with another occasionally-sarcastic female character, who was even suggested to be in a relationship with the same character, at least until she was Killed Off for Real. Her other traits were added to a previously-existing background character, who occasionally takes Don Flack's place. Later, a new recurring female detective was brought into the series and appears to be a Suspiciously Similar Substitute for the original Suspiciously Similar Substitute. She even became Flack's new love interest. All three actresses looked similar as well, especially the last two.
Dad's Army introduced Private Cheeseman as a substitute after the sudden death of James Beck, who played Walker. The character fast became a Scrappy and was written out after only one season.
After Edna Garrett's departure for her own spinoff (The Facts of Life), she was replaced as the Drummonds' housekeeper with Adelaide Brubaker...who was substituted, in turn, by Pearl Gallagher.
Mrs. Garrett was eventually substituted herself on The Facts of Life by her sister, Beverly Ann Stickle.
An interesting exception can be found in A Different World. Originally it was a star vehicle created for Lisa Bonet by Bill Cosby's production house, but after Bonet's 1988 pregnancy forced her from the program after the first season, no substitute for her was cast. Instead, it became an ensemble show, and eventually two minor characters — Dwayne Wayne and Whitley Gilbert — evolved into its real stars and carried the show for five more years.
Averted by PC Penhale for PC Mylow. Mylow was a quirky but competent constable. Penhale started out somewhat like this, only with more extreme quirks. Originally he had narcolepsy and agoraphobia as a result of a head injury, but both of these ended up fading, and he instead acted more like a small boy who was pretending to be a constable.
Originally Pauline for Elaine, though since Pauline has run for three seasons now she has a rather well developed, unique character.
When the anonymous black sheepdog disappears, Joan gets a dog that takes just as much an unwelcome liking to Martin.
Susan, Vicki, Dodo, Victoria and Zoe, while not identical in personality, all fit a "surrogate granddaughter" model in their youth, innocence, and relationship with the Doctor (with Dodo noticeably similar in appearance to Susan and in fact one of the actresses considered for the role, though the actress was not cast for this reason alone). From the point that Ian and Barbara were both replaced by Steven, the rest of the sixties saw a stable companion model of a young heroic male and attractive young female as counterparts to the older Hartnell and the slightly old Troughton.
In the main exception of the decade, Polly and Ben were a pair, and quickly were supplemented with Jamie, the new version of the young heroic male (due to Jamie's character being a last-minute addition). Polly and Ben left after Jamie's A Day in the Limelight story. Jamie's last-minute addition did end up resulting in him briefly having to substitute for Ben in a few of his early scenes as a companion, most infamously the scene of him slapping Polly out of a mental breakdown in "The Underwater Menace".
This also overlaps with Composite Character Ian and Barbara (Ian noble and snarky, Barbara clever, worry-prone and occasionally prickly) left and were "amalgamated" into Steven, an Action Hero like Ian but with a personality similar to Barbara's (in fact, "Galaxy 4" was originally written for Barbara and gives Steven her dialogue with only a few changes).
The Doctor's regeneration was designed specifically to avoid this. Originally there were no plans for him to regenerate he wasn't even designated an alien. That only came about when William Hartnell had to leave the show due to health issues. A producer thought it would be a novel idea, and thus the Doctor as we know him was born.
The original plans for Season 7 had Zoe as the Third Doctor's companion; soon the producer decided she should be written out as part of the show's heavy Retool and so they created Liz, a similar Hot Scientist, to replace her.
"The Invasion" is virtually a direct sequel to "The Web of Fear", but has sewer-dwelling Cybermen invading London substituting for Underground-dwelling Yeti invading London, and replaces Professor Travers and Miss Travers with a similar Mad Scientist and Beautiful Daughter pair. This was because the producer fell out with the creator of the Yeti and the Traverses and wanted to pay them as little as possible. The one returning character created by them is Colonel Lethbridge-Stewart because Douglas Camfield wanted Nicholas Courtney back and having a Suspiciously Similar Substitute played by the same actor would just be begging for a lawsuit, and even he gets a promotion to Brigadier and is mostly referred to by that rank from that point onward not just in the serial, but the show as a whole, even in the few allusions to him in the Revival Series.
The Nestene Consciousness which debuted in "Spearhead from Space" is one to the Great Intelligence of the Troughton Era. Both are (mostly) disembodied gestalts seeking to conquer Earth who rely on partly disguised robotic servants to operate, but the Nestenes use animated plastic dummies instead of robot yeti.
Prop example the Fourth Doctor started using a "secondary console room" at one point, designed to fit the gothic motif he was swiftly developing, which had a chapel-like appearance complete with stained-glass windows and gorgeous real wood paneling on everything. However, the BBC stored the set poorly and the wood warped and cracked, forcing the Doctor to revert to the previous console room set, with a Hand Wave about him redecorating the secondary console room to look like his previous one. This also serendipitously coincided with the Doctor's characterisation going in a Lighter and Softer direction, the result of Mary Whitehouse raising enough of a fuss about the show's increasingly Darker and Edgier direction that producer Philip Hinchcliffe got fired in favour of Graham Williams, whose work on the show was under constant orders to keep it kiddie.
Facially deformed time-travelling Diabolical Mastermind Magnus Greel in "The Talons of Weng-Chiang" was originally supposed to be the facially-deformed incarnation of the Master from "The Deadly Assassin", as the story was planned as a direct sequel to it and was even written by the same man. Due to its close proximity to that serial, however, it ended up mutating into something else. Remnants of that idea include both being hammy, vampiric serial killers on the run with a time machine, dying, and desperately looking for a way to cheat death. Magnus even talks about "regeneration" a few times.
Kamelion in "The King's Demons" was conceived as a successor to K-9, just not looking like a dog.
The Toclafane mutated, insane, Omnicidal Maniac humanoids dependent on heavily-armed miniature tank cases to survive were created as a substitute for the Daleks if the revival show could not get the rights to use them, as the negotiations with Terry Nation's estate were going badly. "Dalek" (titled "Absence of the Daleks") would have revolved around the audience expecting to find a Dalek, but the creature instead being the last Toclafane, the race that wiped out the Time Lords. "Bad Wolf" and "The Parting of the Ways" would have been the conclusion of their Story Arc and revealed that they were in fact humans from the future. The final version of Series 1 did use Daleks in this role, but the Daleks encountered in that story were built from mutated humans like the Toclafane; while somewhat left-field to a viewer starting with Series 1, the twist is not without precedent in the Classic Series. The Toclofane later showed up in Series 3, with their plot twist still making it into the series but in an even dourer context.
Howard Attfield, who played Donna Noble's father in "The Runaway Bride", died during the filming of Series 4, having just finished his scenes for "Partners in Crime". Rather than leave his one appearance there as-is and try to skirt around his absence for the rest of the season, the producers decided to have his scenes reshot with Wilfred Mott (Bernard Cribbins), who had been created as a one-off guest character in "Voyage of the Damned" and was promptly retconned as Donna's maternal grandfather.
This was not the first time Cribbins played a Doctor Who Suspiciously Similar Substitute; in the second of the 1960s non-canon movies, Daleks' Invasion Earth: 2150 A.D., he plays Special Constable Tom Campbell, who replaces the movieverse version of Ian Chesterton who appeared in the earlier movie Dr. Who and the Daleks. In the same film, Louise, the Doctor's niece, is introduced as an almost identical replacement for movieverse Barbara.
Early plans for Series 4 had a character called Penny Carter stepping in as the new companion, "as much like Donna Noble as I can get away with" according to writer Russell T Davies, due to his assumption that the actress who played Donna in a one-off appearance, Catherine Tate, would not agree to return in a regular role on account of being quite popular and busy. When Tate actually agreed to do the show after all and Donna became the full-time companion, Penny Carter did appear as a minor character, spending almost all of her screen time complaining in Donna-like fashion.
BBC Executive Meddling really, really wanted Matt Smith's Eleventh Doctor to be as much like David Tennant's Tenth Doctor as possible, fearing a more unusual character would not be as relevant and popular; there had even been discussion of outright re-cancelling the show, this time for good. The original proposed outfit for the character even followed a similar "'90s indie kid" aesthetic by way of a pirate outfit, but Smith strongly disliked it. The eventual character was more similar to the Tenth Doctor than many other Doctors over the years had been to their predecessors being also a young, romantic figure with a tendency to ramble and a lot of suppressed angst but different enough to change the whole feel of the show. In particular, Smith's reinterpretation of the role took much more from Patrick Troughton's portrayal of the Doctor than any previous actor; most previous incarnations of the Doctor were made to directly contrast their immediate predecessor, and most portrayals of the role since 1982 were characterized in direct response to the popularity and omnipresence of Tom Baker's incarnation.
"Amy's Choice": Some people have wondered if the Dream Lord, an Enemy Without of the Doctor, is one for the Valeyard, villain of season 23's "The Trial of a Time Lord" arc.
River Song is one to Captain Jack Harkness. Both are reoccurring on-off companions who the Doctor has difficulty trusting, both are time travelers much like the Doctor and have used vortex manipulators, and both are paradoxical in nature (much like the Doctor). Captain Jack is immortal and is a living fixed point-in-time, while River is a half-Time Lord whose entire life is a Stable Time Loop. The names they are usually known by are both aliases, and both of them are Anti Heroes in their early (chronological) appearances before reforming after spending time with the Doctor, and both are Extreme Omnisexual and have dated members of various species and genders.
"A Good Man Goes to War" was supposed to include Captain Jack as part of the Doctor's army, but John Barrowman was unavailable and so the character of Vastra was created to take his role possibly why it's only in that story that Vastra shows any sexual interest in men, being exclusively lesbian otherwise.
"The Time of the Doctor": Tasha Lem is so similar to River Song that some fans speculate that she's a regeneration of her. However, dialogue in the episode plus the fact that Tasha technically dies in the episode, being replaced by a Dalek duplicate albeit with her memories and feelings for the Doctor retained, a complete contradiction of River's fate tends to suggest otherwise.
The web game The Doctor and the Dalek replaces the brain-damaged "good" Time War Dalek the Doctor cutely nicknames Rusty (from "Into the Dalek") with the brain-damaged "good" Time War Dalek the Doctor cutely nicknames Lumpy. This is probably because fitting Rusty into the plot would be begging for problems.
"The Pyramid at the End of the World" features the Secretary-General of the UN and some soldiers from opposing armies take on the role normally reserved for UNIT. Kate Stewart (and presumably UNIT) was originally supposed to appear, but a scheduling conflict with her actress prevented it.
The Monks from the "Monk Trilogy" are Reality Warpers that need someone to ask them to use them; their entire plan revolves around tricking someone into giving them this consent. This is very similar to the M.O. of the Trickster from one of the spin-offs. They also shoot lightning, use religious imagery, can change memories and dress in Earth clothing, much like the Silence. In this case, however, it was less the result of unfulfilled intentions and more the result of Steven Moffat having to rush out the trilogy under the highly unusual, exceedingly tight, and horrifically tragic constraint of him having to care for his dying mother; at one point he was stuck writing the scripts for those episodes at her bedside.
Torchwood did this in Children of Earth with Lois, who fills the role Martha was going to play had Freema Agyeman been available. Subverted in the same miniseries when a character who seems like he's being built up to be a substitute for Owen suddenly shoots Jack in the back, and then gets shot himself. RTD says this was intentional because he thinks it's a disservice to characters to outright replace them with a Suspiciously Similar Substitute.
In the show's single, rather obscure, straight example, the Ancient Lights in "Secrets of the Stars" are a slightly-altered version of the Mandragora Helix from the 1970s Doctor Who story "The Masque of Mandragora". Originally, they were intended to be the same entity, but it was decided that it would be too obscure a continuity reference even by Doctor Who universe standards.
Downton Abbey, particularly in later seasons, seems to run on this trope:
An ambitious redhead that doesn't want to stay in service but go out and make it big: Gwen, replacing Ethel. Although there are some differences: Gwen's ambition ran only to the much more realistic goal of becoming a secretary; Ethel wants to be a movie star. And Gwen actually works toward her goals (with some help from Lady Sybil), while Ethel seems to think she should just be handed them. In turn, the ends for each of their characters are also very different.
After Sybil's death, Rose seems set to take her place as the upstairs "modern girl", although, in true M*A*S*H fashion, there are clear differences between their characters (Sybil was an idealistic reformer and Rose is a party girl).
After William is killed in World War I, Season 3 brings us Alfred: tall, fair-haired, awkward, and a potential love interest for Daisy.
It takes a while to determine who fits this role most closely, but by the end of Series 4, it appears that Charles Blake is turning out to be this regarding Matthew. He and Mary start out with an initially hostile relationship, then share a sweeter moment or two, and by the end of the season wants to marry her. Sound familiar?
Sarah Bunting has strong opinions, particularly where politics and class are concerned, likes helping people, and is attracted to Tom, much like the late Sybil.
Drop the Dead Donkey replaced Alex, the one sensible person in the Globelink office, with Helen, a virtually identical character, at the end of the second series. Both of them even had one-night stands with Dave (despite Helen being a lesbian).
Loren's sister Olive disappears between seasons without any explanation (although later, we learn she died of spotted fever during a cattle drive on the Goodnight-Loving Trail). In her place, his sister-in-law Dorothy (whom he was courting before she ran off with another man, leaving him to marry her sister) came to town, fleeing the abusive husband she had ditched Lauren for, and assumes the same role as Olive had as Mike's friend and confidante.
Emma for Myra, as they're both cut from the same Hooker with a Heart of Gold mold. Both of them also wanted a career instead of being a housewife after they had stopped working as prostitutes.
Cloud Dancing was not the first character Larry Sellers played. In the pilot, he played Black Hawk, named in the credits only. Because of the way the show got remodeled after the pilot and the fact he was not named onscreen, his character was essentially retconned into Cloud Dancing.
Due South did this surprisingly well, mixing in a bit of Sister Becky. One character is sent away "under cover" while the main character is out of town. The replacement is introduced as someone pretending to be that character, in order to maintain his cover. The replacement is almost nothing like his predecessor, with almost everybody except Fraser seeming to be unaware of this.
Coy and Vance replaced Bo and Luke Duke. They were such substitutes, they even had the same hair color. The following season Bo and Luke were brought back, and Coy and Vance were never heard of again.
Deputy Cletus Hogg, although his initial appearance on the show preceded Enos' departure for his own series, and he was allowed to stay on even after Enos returned.
Roscoe was also replaced briefly by two different sheriffs — including The Other Darrin himself.
Seen repeatedly in Gene Roddenberry's Earth: Final Conflict, due to the show's unusually high cast turnover rate. In fact, the only character to last through all 5 seasons was series villain Agent Sandoval.
Many new medical students and interns were introduced in the plucky Naïve Newcomer mold of CarterLucy, Gallant, Neela, even Dr. Wise in the series finale. Justified given the series premise: medical students whove never encountered a busy urban ER before are likely to react the same, and given that County is a teaching hospital, it makes sense there would be a revolving door of them.
After Doug Ross' departure, he was essentially replaced by three characters that harbored his best or best-known qualities. The obvious designated successor was Luka Kovac, a brooding hunk with allusions to a mysterious, tragic past, a yearning for Carol, and an impulsive streak that turned self-destructive in subsequent seasons. But if that werent enough, the writers also added Cleo Finch, a skilled and dedicated pediatrician, to fill in for Doug as Designated Pediatrics Person, and Dave Malucci, a brash, reckless rule-breaking resident with a Berserk Button regarding child abuse, not to mention a once-mentioned, but never explained kid and a hatred for Kerry Weaver.
After Kovac became ER chief and a steady presence in the ER instead of a self-destructive one, the writers introduced new characters to again fill the brilliant Lothario role in the ensemble. These characters also shared Rosss well-known qualities: Tony Gates, a reckless paramedic-turned-intern with a penchant for rule-breaking (and also a kid), and later, Simon Brenner, a commitment-phobic womanizer.
Abby Lockhart, twice over. First introduced as Carol's OB nurse during her labor, Abby shows up a few episodes later as a third-year medical student, just in time for fourth year medical student Lucy Knight to get killed off. For the rest of that season, Abby fills the designated medical student role in the ensemble. Then, after Carol leaves, Abby becomes the main nurse character in the ER, picking right up where Carol left off: not only did she immediately start dating Luka, Carol's ex (and aforementioned Doug Ross replacement), but she was even given the aborted nurse-to-doctor storyline, complete with a speech about preferring nursing to medicine. That said, there were some differences in this plot: Carol had always been an RN but decided to study for and take her MCATs just to see if she could pass them. Although scenes were filmed with Carol starting medical school, actress Julianna Margulies was unhappy with the storyline as Carol had always been passionate about nursing and she felt it was out of character for her to switch careers. By contrast, Abby was introduced as a wannabe doc who took nursing shifts to pay for med school. She dropped out not long after her introduction due to lack of funds, but always intended to go back and finish, which she eventually did, becoming a fully-fledged doctor.
Immediately after Abby returns to medical school, shes replaced as ER nurse with Sam Taggart, another nurse with a messy personal life (who dates Luka for a season and a half to boot).
After Peter Benton left, Greg Pratt was introduced as the next arrogant resident who doesnt think he has much to learn, which was Bentons role at the beginning of the series. Character Development taught both that they did, in fact, have much to learn.
In general, the shows main ensemble hinged on six core roles: Moral Compass, Brilliant Lothario, Caring Female Doc, Stressed Nurse, Awkward Nice Guy, and Arrogant Doctor. (In order, the first season had Greene, Ross, Lewis, Carol, Carter, and Benton in those roles.) As the show went on and the ensemble became more crowded, some roles were split across multiple characters, and characters stayed on the show but swapped roles in the ensemble (e.g., after Greene's departure, Carter moved up from Awkward Nice Guy to Moral Compass, with the Awkward Nice Guy role going to Gallant for a while). Later seasons also added new roles into the mix: Newbie Medical Student/Intern, Plucky Female Surgeon (Corday, Neela), Stickler ER Chief (Weaver, Moretti, Banfield), and Doctor Nobody Really Respects (Malucci, pre-character development Morris).
Everwood, for some extent at least: Linda and Amanda are both facing a tragedy of sorts, both feel uneasy around Nina (foreshadowing, much?) and both have a similar relationship with Andy: the rocky start, people against the affair, having a hard time fitting in Andy's family life, and finally breaking up over something directly related to the aforementioned tragedy. Amy's best friends, Laynie and Hannah (who never appeared simultaneously, although they'd be best friends themselves in Grey's Anatomy, same actresses, different characters), also share some traits: tragedy again (the common denominator for everybody in the show), introverted, both have an older brother (one of them dies and the other has a strong chance of inheriting Huntington's), both are somewhat "dark" and both girls click with Ephram instantly (Laynie actually dates him, Hannah is more a best friend / neighbor / like sibling type). Last but not least, Stephanie is in many ways a short-lived Madison II (college-girl, very different from Ephram, great with Deliah, kind with Amy in spite of her (Amy's) jealousy).
After Zhaan dies, she's replaced by Jool who fills the same role as The Smart Guy but is purely scientific rather than spiritual and is much more abrasive in personality, while Stark tries to take over Zhaan's spiritual role (with mixed results.) When Jool leaves, her direct replacement Sikozu is a bit more similar in personality to her but much more competent and calculating. At the same time, Noranti is introduced as a replacement for Zhann and Stark's mystical/spiritual role, but more morally ambiguous than Zhaan was, sometimes being downright sinister. As well as replacing the missing Stark's allotment of awesome.
One episode even featured a group of suspiciously similar substitutes. Escaped prisoners from Peacekeeper custody on a Leviathan transport pod, a Scarran strong guy (reflecting D'Argo's Proud Warrior Race Guy), a Nebari androgyn (hermaphrodite, mirroring Chiana's nonconformist), a female Hynerian, and a captured Peacekeeper tech (reflecting Aeryn's initial unwilling accompaniment of Moya's crew, as well as looking similar to Crichton and being in a similarly mistrusted position.)
Lady Felicia, the well connected, wealthy, somewhat scandalous member of the peerage is replaced in season six with her niece Bunty, who, though much younger, is also a well connected, wealthy, somewhat scandalous member of the peerage, and serves Felicia's role as a foil to the scrupulous Mrs. McCarthy.
Every few years, the inspector of Father Brown's parish is replaced. Generally, the inspector starts out disliking or actively discouraging Fr. Brown from solving crime, but grudgingly grows to allow him his insights when it's proven that he finds the murderers. Usually at the end of a season or two, the inspector is replaced with another skeptical police chief and Fr. Brown has to prove himself all over again over the next season, enabling more conflict in the story.
Frasier: This trope is neatly deconstructed/lampshaded with Mel Karnofski, Niles' Romantic False Lead between divorcing Maris and getting together with Daphne. Mel is a blatantly obvious slightly-milder carbon-copy of Maris (or rather, Maris's actions and descriptions given a more subtle form and voice), paralleling her in everything from being a manipulative and domineering Jerkass to her hysterical, unstable, mood-swinging, and obsessively fussy and neurotic behavior — and Niles is unable to see it. Frasier outright tells Niles that he's repeating a horrible pattern (Maris was quite emotionally abusive and generally had an adverse effect on Niles' mental state), and speculates that he's just jumping at the chance for someone comfortingly familiar because Daphne is getting engaged and he (apparently) no longer has a chance with her.
In Frontline, each season features a new Executive Producer, all of whom are equally amoral but manipulate people in slightly different ways.
Missandei to the late Irri. In the books, Irri is still alive, but Missandei continues to act as an adviser as well as a handmaiden.
In the series finale, Bronn has essentially become the new Littlefinger. A Master of Coin who is also a corrupt, social-climbing, Nouveau Riche noble and an aspiring pimp who pointedly espouses a belief that the strong thrive over the weak. His sleaziness also disgusts the more morally principled of the Small Council such as Davos and Brienne.
Ser Davos becomes one to the late Ned Stark — a Baratheon king's most trusted friend who acts as The Consigliere and can be trusted to tell him what he doesn't want to hear. The key difference is Davos is about a million times more aware of the cutthroat climate of Westeros.
Olyvar to Ros. After her death, he takes over the role of the show's main prostitute, provider of Fanservice, and receiver of Sexposition.
After the first Lady Frey is killed at the Red Wedding, the new Lady Frey is another plain-looking teenage girl - seemingly younger than the previous one - who says or does absolutely nothing but idly stand next to her disturbingly old husband through her whole scene while looking quite miserable and scared. He did say he'd "get another one" right before his last wife's death...
In The George Lopez Show, Carmen is replaced with Angie's niece Veronica Palmero because of creative differences between Carmen's actress, Masiela Lusha, and George Lopez. Veronica is the same as Carmen, only more shallow and with a sadder story.
Get Shorty: In the first season, Nathan Hill is a no-name actor who gets his big break on The Admiral's Mistress. In season 2, Nathan is never seen again outside of movie footage from the first season, but we're introduced to David Oumou, a no-name actor who got his big break in a supporting role on The Admiral's Mistress.
Get Smart (the original show) did this for the episode "Ice Station Siegfried." Don Adams had a root canal and couldn't be there for the shooting of one episode, so the writers created Agent Quigley, who acted exactly like Maxwell Smart and was also attracted to Agent 99, to replace him for one episode. He was never seen nor mentioned again. Incidentally, the script for "Ice Station Siegfried" was so bad that Adams purposely scheduled his dentist appointment so that he would miss the filming of it and not another Season 5 episode.
In season 3, many of the original cast (and the one with the largest, most vocal sub-fandoms) graduated and became recurring characters. In their place is a league of hip, young freshman replacements who suspiciously resemble the first generation of glee clubbers;
Marley Rose is just like the original Rachel Berry; Heterosexual, Caucasian, skinny, pale brunette with a wailing Broadway voice is made the captain and lead singer of the New Directions. She also has a crush on a member of the football team who seems to be completely out of her league and is dating a nasty blonde cheerleader who hates her, which causes ominous wangst. And despite her being unpopular the football player has a strange affinity for her, and Rachel is the main protagonist season 1-3 whilst Marley is the main protagonist in season 4.
Kitty Wilde and Quinn Fabray's similarities are even lampshaded in the series; They're both (for at least a brief time) head cheerleaders, both Caucasian, heterosexual, and blonde with a strange, inconceivable hatred for the main heroine who has never done anything to them. They are both popular but implied that their "friends" don't really like them (Quinn's falling out with Santana/Kitty saying she really just wants friends). They're also dating the football player as an obvious Romantic False Lead, but seem to be using them for popularity at the best of times and get jealous and possessive over them even talking to other females in a purely platonic sense. It isn't helped by the fact that Kitty worships Quinn and constantly gushes about how she wants to be just like her. Or the fact that Sue dubs Kitty "A young Quinn Fabray, except not pregnant, manically depressed and in/out of a wheelchair", which crossed the Dude, Not Funny! territory for some viewers with experiences of that nature. They both have high, wispy voices too.
They don't even try and hide the similarities between Puck and Jake; Both from a broken home in which they didn't know their father, they both play/ed for the football team and have a big reputation as trouble makers and womanizers (To the point where Unique feels it necessary to break into an improv Britney Spears number to prove it). They both have strong, baritone voices and start off dissing the glee club and disputing it, before slowing warming up to the idea of singing and dancing on stage. They both are implied to see themselves as losers and both have a below-average IQ and are popular. Oh yeah, and they're half brothers. This is later deconstructed when Jake says he doesn't just want to be seen as a failure because his brother was and that there's more to him than his genes. He's having a tough time proving it, though.
Unique/Wade is a big fan of both Kurt and Mercedes, so it's a good job the fandom refers to her as their lovechild from the future. When it comes to Unique being like Mercedes, they share body-shape and race, as well as having "Big belter" Whitney-esque voices and their main superlative being "Sassy diva". And being The Lancer to the main heroine of the series (Rachel/Marley). They both campaign for more solos throughout their airtime too, often claiming that their voices are neglected. When it comes to Unique being like Kurt, they have both suffered prejudice and bullying over their sexual orientations (Kurt is gay and Unique is transgender), as well as auditioning for a big role in the annual Mckinley musical and for some reason or another not getting to do it. They also act as a Pet Homosexual to Rachel/Marley. They both show explicit interest in fashion and style and are quite eloquently spoken for teenagers.
Ryder Lynn takes the role of Finn. Finn is even the one who recruits him for the glee club. Both are football players, who are well meaning if a little dull. Ryder is even part of a love triangle involving Marley (the Rachel stand in) and Jake (the Puck stand in). He also borrows elements from Sam, as the two were both dyslexic. This is somewhat fitting considering that Sam was something of an Expy of Finn.
Bree is a character introduced in season five and seems to take the role of Santana. Both are the Token Minority on the cheer team and are both Alpha Bitches. She's even outright called "the new Santana Lopez".
Good Eats has an episode about making substitutions in a recipe, whether it's because one of the diners is allergic to an ingredient, personal preference/Rule of Cool, or not having an ingredient on hand (and not wanting to make a trip to the supermarket). It's revealed at the end that the episode was narrated by A.B.'s Evil Twin, B.A.
After Kalinda's departure from The Good Wife a new character is introduced right away; Lucca Quinn, aside from the somewhat physical similarity, she became Alicia's best friend and Cary's Love Interest in one season, roles previously held by Kalinda. She also becomes, as Kalinda was, Token Minority.
Happy Days, upon the leaving of Ron Howard, brought in a family friend named Roger who replaced the "straight-man" tendencies of Richie.
After Howard Hesseman left Head of the Class in 1990, Billy Connolly's character substituted him for the show's final season, but the two characters' personalities could not have been more different. Whereas Hesseman's Mr. Moore was a serious mentor for the kids, Billy was a joker who often joined in on the kids' shenanigans, and even let the students call him by his first name.
In Heroes, West's relationship with Claire leaves him as little more than a straight version of Zach. The writers tried to cover this up by giving him the power of flight/levitation but his lines and role as a foil character made it obvious.
Carried out with style by British fantasy show Hex, where new girl Ella, an experienced witch, shows up at the start of the second season and by the end of the second episode has stabbed original lead witch Cassie and taken her place as the show's main character. She goes on to have an almost identical doomed relationship with demon spawn Malachi that Cassie had with demon Azazeal in the first season. To round things off, Malachi is Cassie and Azazeal's magically-aged son.
The long-running Australian sitcom Hey Dad..! continued for a 13th and 14th season after the titular character left, with a family friend serving as an unofficial father figure. Over its long lifespan, the show had a nearly complete changeover of cast, with replacements alternating between thinly-disguised substitutes and unexplained Other Darrins.
Hill Street Blues — When Michael Conrad died after Season 3, his Sgt Esterhaus was replaced with Robert Prosky's Sgt Jablonski. Each had catchphrase to close out the briefing at the top of each episode. However, where Esterhaus had been warm and fatherly ("Let's be careful out there"), Jablonski was much harder-edged ("Let's do it to them before they do it to us").
Sergeant Baker replaced Sergeant Kinchloe as 'radio operator who happens to be black' on Hogan's Heroes in the final season. Unfortunately, unlike Kinchloe, Baker didn't have much characterization apart from 'radio operator who happens to be black' and wasn't the most satisfying of replacements.
While the original ducklings still appear on House, their roles as, well, ducklings have been replaced. By Taub, Kutner, and Thirteen, who are superficially similar to the original three characters. Their exact personalities don't line up but House admitted that he hired them based on the same dynamic he had with the earlier team. Interestingly enough for the trope, the previous actors didn't leave the show, they just added more cast.
In House of Anubis KT came in after Nina had left (as Nathalia quit to focus on school work.) Many fans had this reaction at first, considering both of them are from the United States, were raised by a grandparent, and have a destiny to do with Ancient Egyptian Mythology. Some of the characters even seemed to believe this at first.
When Mickey left Hustle after season 3, Billy was introduced as a Suspiciously Similar Substitute for Danny, with Danny taking up Mickey's role. In season 5, Mickey's back and the Danny/Billy role is taken by Sean, with his sister Emma as the new Stacie.
iCarly (2021): Jennette McCurdy refused to reprise her role as Sam Puckett from the original iCarly, so the character was written out of the show. Two new characters were introduced to fill the void left by Sam as well as Gibby (Noah Munck also didn't return). One was Carly's new best friend Harper Bettencourt, who has little in common with Sam. The other is Freddie's stepdaughter Millicent Mitchell, who is every bit as sarcastic and manipulative as Sam was, including her hot and cold relationship with Freddie. The biggest differences between Sam and Millicent is that Millicent is younger, lacks Sam's propensity towards violence and arguably has more redeeming qualities.
In the second season of In Treatment Luke and Bess, a couple whose divorce was harming their son, were clearly substitutes for Jake and Amy in the first season. This is because, in the Israeli series the show is based on, the corresponding couple's arc continued into the second season.
There have been seven Iron Chefs: Chen Kenichi (Chinese), Hiroyuki Sakai (French), Masaharu Morimoto (Japanese), and Masahiko Kobe (Italian) are the ones American viewers are most familiar with. The dubbed version tried to push the idea that Morimoto was the direct successor to Rokusaburo Michiba, the original IC Japanese. In truth, Morimoto was a substitute to a substitute: Michiba's replacement was Koumei Nakamura (Who can be spotted behind Chairman Kaga in the opening credits, where Kaga is standing behind the pile of strawberries). There's also the original IC French, Yutaka Ishinabe (whose portrait can be spotted in the opening panorama).
Jessica Jones (2015) was unable to use Carol Danvers, Jessica's best friend from the comics, because the character was tied up in Captain Marvel. To replace her, the writers brought in Trish Walker to serve as Jessica's best friend. Additionally, instead of being a redhead, Trish now has long blond hair as Carol did in the comics.
Carla Borrego for Maddie Magellan in Jonathan Creek. And then Joey Ross for Carla. All female investigative journalists (of a sort; Carla presents a Crimewatch-style TV show and Joey runs a paranormal website) who march into situations and take charge, leaving Jonathan to fade into the background, and are eternally exasperated with him. The main difference with Joey is that her relationship with Jonathan isn't based on UST.
In Judging Amy, Dan Futterman played Vincent Gray, Amy's highly intelligent younger brother, in episodes 1 through 51, when he left the show. He was soon substituted by Kevin Rahm in the role of Kyle McCarty, Amy and Vincent's highly intelligent second cousin who had much of the same intelligence and mannerisms as Vincent. With Kyle's introduction, it was explained that Vincent and Kyle had been roommates and spent much of their younger years together. Vincent returned to the show in episode 100, and effectively reverse-substituted for Kyle who left the show in episode 118. Vincent remained for the rest of the show's run.
The original series was forced to do this with Takeshi Hongo/Kamen Rider 1 after Hiroshi Fujioka broke his leg while attempting a stunt. Unlike many examples of this trope, however, the replacement character (Hayato Ichimonji/Kamen Rider 2) is remembered fondly by the fanbasenote In fact, a lot of the iconic tropes of the Kamen Rider franchise, like invoking the transformation by posing and shouting "Henshin!", began during Ichimonji's tenure and has become just as much a fixture of the franchise as his predecessor, and when the former returned to the show, the two are often paired under the nickname "Double Riders."
Kamen Rider Decade did this to most of the cast of the shows they visited, using the conceit of Alternate Universes. However, while most of the characters got substitutes, several of the original actors gladly returned to reprise their roles (even if they were alternate universe versions). The most stand-out example is Kamen Rider Hibiki, where most of the secondary cast came back, but the actors who played the show's two stars (Hibiki and Asumu) didn't.
The old-school Riders had a recurring, cross-seasonal ally named Tobei Tachibana. He started out as Hongo's friend who ran the motorbike racing club but got more and more involved with things Rider-related just due to being close to the guys trouble followed most, becoming something of a Badass Normal. When Powers That Be decided to bring the character back in Kamen Rider: Skyrider but the actor declined, the Tachibana role in that and the following series went to the nigh-identical Genjiro Tani. His personality and role were exactly Tachibana's, and sometimes past Riders talked to Tani as if they knew him much better than they did as if scripts with Tachibana in mind had already been written. They really shoulda gone the Magic Plastic Surgery route.
Knight Rider replaced Wrench Wench Bonnie Barstow with April Curtis for the second season, then brought back Bonnie the next year.
Knots Landing: In Seasons Ten to Twelve, Valene's aunt Virginia "Ginny" Bullock is one for her own sister Lilimae, who left in Season Nine.
Done by necessity quite a lot on gentle old dears' British comedy Last of the Summer Wine, as elderly cast members die off with inconvenient regularity. (The last member of the original regular cast, Peter Sallis, died in 2017 at the age of ninety-six, seven years after the show was finally cancelled.)
Law & Order has always had six main characters: two detectives, their chief, the DA, the executive assistant DA, and a regular assistant DA. Given that the series lasted for 20 seasons, all six roles have been substituted as actors move on, some of them several times over. It also helps that the show is heavily story-based, and not too dependent on characterizations.
The earliest example occurred in the first episode of Season 2. No sooner was Season 1's Max Greevey (George Dzundza) gunned down that the credits start and we see Paul Sorvino's name in the credits. Sorvino's character, Phil Cerreta was a similarly overweight, older detective whose sense of values conflicted with Logan's more reckless tendencies, especially in this episode.
Law & Order: Special Victims Unit has seen this a few times; while actress Mariska Hargitay was away due to pregnancy, her character Olivia Benson was briefly replaced by Dani Beck, who spoke fluent French, physically assaulted perps without consequence, was famous for her effectiveness in fighting crime, had a cool personal PDA/GPS system that she flashed around a few times, and had the romantic affair with Elliot that fans wanted him to have with Olivia. In general, the fandom doesn't miss her.
The ADA's in SVU get replaced. Most people didn't mind the Alex Cabot replacement by Casey Novak (they have very different personalities), but the ADA who replaced Novak for Season 10 was a mediocre blend of both of them, with a dash of Informed Ability to boot. "They used to call me the Crusader." Fan backlash led to them bringing back Alex.
Law & Order: UK subverted this, with DS Matt Devlin's replacement Sam Casey being young and good-looking like he was, as well as having an absent/abusive father, but being far more hot-tempered (Matt's temper was generally limited to certain issues, Sam had a short fuse about everything), and rebuffing Ronnie's efforts at mentoring and friendship, in stark contrast to Matt, who clearly cherished the surrogate father that he had in Ronnie. His replacement Joe Hawkins fell somewhere in between.
Jefferson "Jax" Jackson was created to replace Ronnie Raymond as Firestorm after contractual issues made it impossible for Robbie Amell to reprise his role from The Flash.
The writers planned to have Vixen from Arrow join the cast in Season 2, but when Megalyn Echikunwoke was unable to reprise her role due to scheduling issues, a new Vixen named Amaya (the grandmother of Arrow's Vixen) was created to replace her.
On Leverage, Gina Bellman's pregnancy required a hasty write-off of Sophie before she started showing, so she was replaced for half a season by Tara Cole (played by Jeri Ryan).
Lexx couldn't get the actress who played Wist back, so they created a second gorgeous blonde predator with a childlike demeanor in Lyekka.
Nancy Oleson on Little House on the Prairie is a replacement for long-time nemesis, Nellie Oleson. This is lampshaded in the episode where the Olesons adopt her, as Harriet mentions how she looks "just like Nellie" while Nels later ruefully acknowledges that she acts just like Nellie, too.
In season 2, Nixie and Lyla are replaced with Mimmi and Ondina, the former two having left the show. Ondina is clearly the substitute for Lyla, both being prickly, impatient and headstrong (and blonde). Interestingly enough, Mimmi takes Sirenas spot as the compassionate and naive Nice Girl. Because of this, Sirena gets a slight personality change and takes Nixies spot, now being a lot more competitive and confident than she was in season 1.
In season 3, Sirena leaves the show and is replaced with Weilan, who is a lot more similar to Nixie than Sirena was.
The Mandalorian: The title Mandalorian is a mysterious Mandalorian warrior who never takes off his armor, works as a bounty hunter, and has a Dark and Troubled Past due to being orphaned at a young age. He is a very clear stand-in for Boba Fett, the most famous Mandalorian from the films. The most immediate difference between the two is that Boba is a Mandalorian by birth but has little to do with the culture, while the Mandalorian was adopted by the Mandalorians and much more closely connected with their culture.
Trapper was replaced as Hawkeye's bunkmate and partner-in-crime by BJ. Though there are similarities between the characters, BJ was noticeably more laid back than Trapper — and was also a devoted family man, whereas Trapper was routinely (and guiltlessly) unfaithful to his wife. Trapper and BJ also had very different ethical standards when it came to certain medical issues. In one of his last appearances, Trapper cheerfully helps Hawkeye perform an unnecessary appendectomy on Col. Flagg in order to protect a life-saving supply of penicillin. In a later episode, Hawkeye goes to perform a similar unnecessary appendectomy on another colonel, to keep this colonel from leading a bone-headed strategic manoeveur that will pointlessly send troops to their deaths. BJ objects strenuously, and will have no part in the operation, arguing that it's mutilation and a violation of medical ethics.
Col. Blake was replaced by Col. Potter, which was a major subversion. Blake was spacey, had no army background, and lacked real authority. Potter, meanwhile, was army through and through — a stern yet fatherly leader who had a firm grip on command.
When the snotty, arrogant Frank Burns left, he was immediately replaced by snotty, arrogant Charles Winchester. However, the two characters were extremely different. Burns was an incompetent doctor, a charmless nitwit, and a cowardly hypocrite who was easily outfoxed and impossible to respect. Winchester, by contrast, was a first-rate surgeon with a very firm code of ethics. While Winchester's smug demeanour could be off-putting, he was able to be charming when he had to be. He was also very well-educated, smart, and very much a potentially formidable opponent.
Not always inverted, though. Particularly very early in the show, some very minor characters (who would only last a few episodes, and never got much Character Development as a result) are replaced with similarly undeveloped minor characters. This is particularly true of various early-season nurses (who are all basically treated as interchangeable dates for Hawkeye and Trapper) and commanding generals (who are more-or-less interchangeable out-of-touch authority figures.)
One could argue that Sgt. Luther Rizzo (crafty Louisiana goldbricker) is a Suspiciously Similar Substitute for Sgt. Zelmo Zale (crafty Brooklyn goldbricker).
Maverick introduced a Suspiciously Similar Substitute before the star left, in the form of Bret Maverick's brother, Bart. This was principally done in order to accelerate the show's shooting schedule since they could shoot a Bret episode and a Bart episode at the same time. Reportedly, the show's writers had no idea whether a given episode would be a Bret episode or a Bart episode when they wrote it. By the show's end, there were two other Mavericks in rotation, one of them played by Roger Moore. The most suspiciously similar of them all was Brent Maverick, who was introduced shortly after James Garner (who played Bret Maverick) left the show. Not only was Brent's name just one letter off from Bret's, but he was played by Robert Colbert, who bears a remarkable likeness to Garner. When Colbert discovered the producers' plan for him, he rebelled against them, reportedly begging them to, "Put me in a dress and call me Brenda! ANYTHING but this!"
Maverick also did this with recurring roles, noticeably bringing in "Gentleman Jack" Darby to fulfill the same type of competitive friend/adversary function as "Dandy Jim" Buckley. Then Buckley was replaced by "Nobby Ned" Wyngate. All three were essentially the same character: a very sharp-dressing, outwardly smooth gambler who had a long history with the Mavericks, and who would work with (or sometimes against) the Mavericks on their latest scheme — but who would cheerfully switch sides on a moment's notice if the money was right.
Neil Morrissey as Tony Smart from series 2 of Men Behaving Badly, replacing Harry Enfield as Dermot Povey. Since this happened on ITV, and the show only became popular after the third series was taken up by The BBC, most viewers have only the vaguest idea there ever was a Dermot Povey. (In one Clip Show, a single scene from series 1 is shown, prompting Tony to ask "Who was that?")
The late '80s-early '90s incarnation of The Mickey Mouse Club turned over its cast a few times. Notables in the mix include Keri Russell (as part of the first rotation of new blood) and Britney Spears (as part of one of the last rotations).
In Midsomer Murders, DCI Barnaby was replaced by... DCI Barnaby (his cousin, who had the same rank and personality, but was played by a different actor). Also, he had already changed his sidekick twice. In fairness, in a number of countries, the series is called "Inspector Barnaby" so the change makes sense.
Season three replaced Daisy, Blaine, and their boss. A number of minor characters are also gone as well. In fact, the only characters who have been carried over from the last season are Rose, The Grand Master, and the school headmaster.
The third series replaced Lenny Bicknall with Frank London, both retired superspies posing as a high school caretaker.
Forms a major plot point in Millennium, "Dead Letters". Frank Black liaised with Jim Horn, a potential Millennium agent. He was almost a near-duplicate of Frank's character type, except he was a bit too much of a Cowboy Cop for the Group's liking. Needless to say, he didn't make the cut.
After Danny gets Demoted to Extra in The Mindy Project's fourth season, Jody (his replacement at the ob/gyn practice) becomes this. Both Jody and Danny are fairly conservative men with some stereotypical traits (Danny is an Italian from Brooklyn, Jody is from the South) that are also romantic interests for Mindy.
In Misfits, all main characters from the first two series have been replaced over the course of series 3 and 4 by characters who occupy similar roles in the ensemble, but have different enough personalities.
Nathan left after Series 2 and was replaced by Rudy, an equally mouthy character who, like Nathan, has the habit of saying outrageous things. Subverted slightly in that Rudy is a more complex character with multiple facets (made literal different people by the Storm).
Simon, Alisha, and Kelly left after Series 3. Series 4 introduced Finn (another socially awkward guy with hidden depths), Abby (another promiscuous party girl with hidden depths), and Jess (Another no-nonsense, rude girl). Note that despite being Kelly's Spiritual Successor, Jess takes Alisha's place romance-wise, and, just like Alisha, starts dating the handsome/athletic guy in the gang (Curtis and Alex, respectively), before ending up with the apparently weirder one (Simon and Rudy, respectively).
Series 4 introduced Alex, the handsome barman, and then killed off Curtis the athletic barman. Alex joined the gang full-time for series 5.
After season 1, team leader Dan Briggs was replaced by Jim Phelps. After season 3, Rollin Hand was replaced by "The Great Paris." Replacements were seamless, since the characters were constantly playing roles within the show, and were purposely written to show a minimum of personality outside their jobs.
In principle, the leader (Briggs or Phelps) chose the team members for each mission from a large dossier of agents. In practice, especially in the early episodes, it was mostly the same team.
The Chick in the Five-Man Band started out as Cinnamon, who was replaced by a parade of guest stars in Season 4, Dana in Season 5, and Casey in Seasons 6-7 (with Mimi briefly serving as a Temporary Substitute). Averted somewhat with Casey, who was not just the femme fatale but also replaced Rollin and Paris as the team's makeup master, since budget cuts required reducing the cast size. The show also attempted to replace Willy with a doctor named Doug, but Willy was Saved by the Fans.
In Monarch of the Glen, the character of Paul Bowman was introduced in Season 4, and subsequently revealed to be the illegitimate half-brother of the main character, Archie MacDonald, Laird of Glenbogle. Two seasons later, Archie gets Put on a Bus to New Zealand, Paul Bowman-MacDonald is made the new laird, and the series carries on as before, including Paul having UST with Archie's wife. (Although it doesn't go anywhere.)
Monk did this when Traylor Howard was introduced as Natalie Teeger, replacing Bitty Schram's character Sharona Fleming as Monk's assistant midway through season 3. The next few episodes were very obviously written for Sharona, with the only real difference in the characters being Natalie calls him "Mr. Monk" instead of "Adrian." (Well, almost all of the time) This gets especially weird when she states that she's never seen Monk's feet like that's a big deal, despite having only taken the job in the previous episode. The point at which the writers ran out of their previous scripts and were able to start creating material specifically for Natalie (mostly involving her dead husband at first) is very, very clear, and happens some time around "Mr. Monk and the Election" or "Mr. Monk and the Kid". Lastly, due to the death of Stanley Kamel (Dr. Kroger), Hector Elizondo has taken on the role of a new psychiatrist for Adrian Monk.
All characters other than the robots had been replaced by the show's end, yet the writers took care to make the replacement (and their interaction with the rest of the cast) different from the departing character. Consequently, there's no real consensus among the fans whether any given replacement was better or worse than the original. It also helps that each replacement actor was either behind the scenes since the start, or with the team for ages before they got in front of the camera, so none of them were really "new."
Joel was a father figure to the bots. His replacement, Mike, interacted with the bots as their equal (at best) and tended to be more overtly sarcastic. The flame wars over which of the two was better are notorious. While the bots see Joel as a father figure, they see Mike as a brother figure and thus are more inclined to mess around with Mike and prank him relentlessly than they would Joel.
TV's Frank was Dr. Clayton Forrester's minion and punching bag; when he departed, he was replaced by Pearl Forrester, Clayton's mom and one of the few people capable of cowing her son into submission. After Clayton departed, Pearl took over as the head Mad and gained her own minions, Bobo and Observer.
TV's Frank himself was a replacement for Dr. Erhardt, who "went missing" after the first season. When watching Earth vs. The Spider and seeing a character who looked a lot like Dr. Erhardt be eaten, Joel was thus inspired to say, "So THAT'S what happened to him!"
The 2017 revival features Kinga Forrester (Pearl's granddaughter) as the new main MAD, with her henchmen, Max (TV's Son of TV's Frank), and Jonah as the new captive forced to watch bad movies.
On MythBusters, Kari Byron went on maternity leave and was replaced by Jessi Combs for a few months. The original Build Team was Kari, Tori, and Scotty (Wrench Wench) who left the show under "personal reasons" and was replaced by the now better-known Grant. And there is also Christine, a "Mythtern" before the Build Team came into play, who directly assisted Jamie and Adam and had a certain resemblance to Scotty.
At the end of Season 2, NCIS agent Kate Todd is shot and killed by Ari Haswari, a Hamas terrorist working undercover within Mossad. Then at the beginning of Season 3, Mossad agent Ziva David, Ari's sister, joins the NCIS team as a Liaison Officer. Ziva resembles Kate physically- both are slim, brown-eyed brunettes. And Ziva quickly picks up Kate's habit of engaging in rivalry, banter, and Unresolved Sexual Tension with NCIS agent Tony DiNozzo. Otherwise, Kate and Ziva are quite different characters, but this is not a case of The Other Darrin.
The fifth season ends on a cliffhanger which implies that Tony, Ziva, and McGee will all be substituted, and, indeed, the sixth season premiere shows Gibbs leading a new team, with establishing shots helpfully indicating which of the previous characters' niches the new agents fit into. Interestingly, the new team has most of the worst qualities of the characters they're replacing—Langer is a meaner Tony, Keating is a wimpier McGee, etc. The trope is then fairly quickly subverted and by the end of the second episode of the season, the team is reunited and back in business.
Subverted in the 7th season opener when the team interviews replacements for Ziva. Two don't live up to their hype, and one came in at the wrong time. Ziva returns at the end, at least physically.
Also subverted when Ziva leaves for good at the beginning of Season 11; her replacement, Ellie Bishop, is nothing like Ziva or Kate.
Subverted in NCIS: Los Angeles. Originally the team was to be headed by agent Lara Macy, played by Louise Lombard, but after apparently she didn't test well with audiences in the pilot, she was replaced by Hetty Lange, played by Linda Hunt. They are nothing alike.
A few from Neighbours, though the straightest examples may be Tom Ramsay replacing his brother Max, and Oliver Barnes being hastily written in to replace his brother Will/Sebastian, even taking over his whole character arc.
On Fox's New Girl, the character of "Coach" (Damon Wayans, Jr.) appears only in the pilot. By the time the second episode rolls around, we instead have "Winston," (Lamorne Morris) another young, handsome, goateed, athletic African-American roommate. The switch is given something of a Hand Wave, with the explanation that Winston is the "real" roommate, and that Coach was just subletting while Winston was off playing pro basketball in a Latvian league. The actual reason for the switch is that Wayans shot the pilot while his ABC show Happy Endings was on the cancellation bubble, and between the pilot being shot and the show being picked up as a full series, ABC decided to renew Happy Endings...Which did the same for Wayans' contract. (However, after Happy Endings ended for real, Coach returned and both characters lived in the loft.)
A rather tragic example occurred in the final season of NewsRadio (and the only example in the whole series- the other character who left was simply Put on a Bus and never replaced). Max was brought in to take over the role that had been filled by Phil Hartman as the over-egotistical Bill McNeil. Unfortunately, shortly after the completion of season 4, Hartman was the victim of a Murder-Suicide by his own wife, and for the final season, Jon Lovitz joined the cast in a similar role as Max. Incidentally, Lovitz had been close to Hartman and joined the cast because he wanted to pay homage to his friend. (This is given a nod in-universe: Dave ultimately chooses Max — out of a broad pool of applicants — because he was a close friend of Bill's.)
Flo replacing the deceased Selma on Night Court. Flo then also died a year later, leading to the younger Roz. (Also on this show, Lana was replaced by Mac, and Liz was replaced by Billie, then Christine).
NYPD Blue is the master of this trope, having replaced Andy Sipowicz's partner three times. Jimmy Smits replaced David Caruso when the latter decided he was too big to do the show. Rick Schroder replaced Smits. Mark-Paul Gosselaar replaced Schroeder. Gosselaar and Schroeder are the best examples here, both having similar physical make-ups and similar character personalities (and even similar histories as respected former teen stars who'd played blond, comic extroverts, then turned to darker drama as mature actors).
Downplayed in Odd Squad. Agents Olive and Otto are replaced with Otis and Olympia, respectively. They have differences, but they are superficial at best. Otis and Olympia are then replaced with Opal, Omar, Oswald, and Orla, who also have stark differences to the previous casts but also have personality traits from them mixed into their current ones, such as Opal's need for perfectionism and Omar's goofy carefree nature.
The series did this in its final season with Pete (Jake Lacy) and Clark (Clark Duke) being immediately lampshaded as the "new Jim and Dwight", due to their resemblance to younger versions of both characters. They did this despite both Jim and Dwight still being around.
D'Angelo Vickers was a very clear "New Michael", and when Andy ended up in the full-time role of regional manager, he, too, started acting a lot like Michael. The crazed superior went from Jan (not the CEO, but the VP of Sales and Michael's immediate superior) to Jo to Robert (with the final CEO, David, being a subversion, but he also had already been seen in the more sane role of COO). The young self-important jackass became Gabe once Ryan left the show, though there, Ryan didn't really develop that persona until replacing Jan as VP of Sales, then kept it even when busted back down to intern, while Gabe's main quirk was that he was technically Jo's liaison to the office, enforcing her will, but had no actual power.
Uncle Albert for Grandad on Only Fools and Horses. More blatant in his first few appearances, in which he was just filling the role that Grandad would have filled if not for Lennard Pearce dying, but he soon started to be portrayed as being more physically capable and less of a Cloud Cuckoolander than Grandad, along with his navy background playing a more important part in episodes.
The Orville: Talla, who replaces Alara, is very similar to her. Not only are they both the same species and gender, but their personalities aren't that different either. So far the only significant difference is that Talla is taller, older and lacks the family prejudice against the military. After just 2 episodes the new character is best friends with the rest of the crew and is sharing relationship advice with them, just like the old one.
Stretch Snodgrass was substituted with his brother Bones in several first and second season episodes of the TV Series. The actor who played Stretch, Leonard Smith, wasn't available.
Mrs. Winona Nestor was replaced by her sister, Mrs. Ruth Nestor in the fourth season of the TV series. The actress playing Winona, Nana Bryant, left the show after only a couple of appearances.
The temporary replacement of Mrs. Davis, with her sister Angela, for a few episodes in the third season of the TV series and contemporaneous radio program. Jane Morgan, the actress who played Mrs. Davis, had suffered a stroke (fortunately, she made a quick and full recovery).
Really head-spinning example from The Paper Chase: When the study group is formed during the pilot episode, one woman is included. In the very second episode, that character's place in the study group, with no explanation, has been taken by another woman, Logan, who remains a major character throughout the series.
According to Word of God, Michelle from Series 3 was created to replace Toni after Toni's actress, Elizabeth Marmur, declined to return to the show.
Sophie's cousin Barney in the fifth series is a fairly obvious replacement for her brother Jamie from series four; they look similar, are both musicians, both obsessed with Jeremy, and Barney even hangs around with Sophie's father for no explained reason.
After the death of Bea Benederet, the mother and hotel manager from Petticoat Junction, June Lockhart was cast as a new town doctor who took up residence in the hotel. Although she was clearly not the girls' mother, and the girls were all well into adulthood by that point, she carried on Benederet's function as motherly advisor and the town's most sensible resident.
Justin from Power Rangers Turbo serves as one to two characters. He is one to Billy's taking over the role as the nerdy Blue Ranger though this is a downplayed example due to the difference in age. He also fills the role of Fred, serving as a Kid-Appeal Character introduced in a movie, though unlike Fred, Justin actually does become a Ranger and sticks around for the series.
They did manage a successful change in Power Rangers Lost Galaxy, where actress Valerie Vernon had to leave due to being diagnosed with leukemia. Originally they were going to take the previous pink ranger and bring her in as a replacement, but when that deal fell through, they took the previous season's reformed Big Bad, Karone, and made her the replacement. In this case, the character was vastly different because she had aspects of The Atoner.
Another successful change was Adam Park, the second Black Ranger. While Zack was fun-loving and energetic, Adam was fairly quiet and thoughtful. Early on, this was all his character had to him, but an ad-lib in The Movie (his dejected "I'm a frog..." when finding out what his spirit animal is) gave him some Woobie points and being the second-longest serving ranger gave him fairly decent character development. He's one of the most popular characters in the series now and the only pre-Disney buyout ranger to appear in the 15th anniversary Reunion Show.
Sarah Page was killed because her actress couldn't continue acting for the show, and was replaced by Jess Parker. However, their roles are very different; Sarah was an expert in mythology and ancient cultures, while Jess is a techie and team coordinator.
Sarah in turn replaced Jenny Lewis, who was an alternate-timeline duplicate of Claudia Brown, played by the same actress but with a completely different personality and role, an inversion of the typical Suspiciously Similar Substitute.
The series has also been through three different leading men and two different tough-guy supporting men. Only three cast members have stayed with the show through its entire run. The leading men are a particularly interesting example of this. With the first switch, the authors went for a genuine attempt to not make the substitute suspiciously similar, and in fact, the character changed the entire tone of the series. When this second leader was in turn switched out they brought in a replacement that was suspiciously similar to leading man number one, up to and including his accent. The tone of the series also switched back, becoming particularly obvious when number two reappeared for one more episode.
Kochanski was this for Rimmer. Others thought Kochanski replaced Kryten, while the latter became Rimmer's replacement.
Also inverted — Rimmer is killed off in the first episode and replaced by a hologram, portrayed by the same actor. Hologram Rimmer was written out of the story in Series VII after Chris Barrie chose to leave the show. He returned in Series VIII to play the revived original Rimmer.
Subverted with Pree, who is obviously set up to be a replacement for Holly, only to turn into the Monster of the Week.
The Red Green Show. The marina owner changed from the reasonably-built but lazy Glen Brachston to the overweight and lazier Dwight Cardiff.
The series appeared to be about to replace Robin as Robin of Sherwood had. Season 3, episode 10 invented a backstory for Robin Hood and Guy of Gisbourne that created a mutual half-brother for the characters. Both Jonas Armstrong (Robin) and Richard Armitage (Guy) were expected to leave the show at the end of the third season, presumably to be replaced by their brother Archer. Then the show was cancelled.
The character of Marian was replaced with Kate...who had the same personality as her predecessor, only blonde and poor (and shrill). The result was cringe-inducing considering that Kate was written as arrogant, impetuous, and initially antagonistic toward Robin, just as Marian was. What the writers failed to realize was that such traits are understandable and endearing in a privileged noblewoman who had been jilted by Robin, but completely nonsensical in a peasant girl who had no reason to be any of these things.
The show inspiredly replaced Michael Praed's Robin of Locksley with Jason Connery's Robert of Huntingdon, exploring both of the two contradictory versions of Robin Hood in the legends - either a salt-of-the-earth yeoman (a free-born smallholder) or a socially-conscientious aristocrat rebelling against the corruption of his class - by making "the Hooded Man" a Legacy Character.
Sabrina the Teenage Witch originally had Jenny as her Muggle Best Friend, only to replace her with Valerie in season 2. Season four then replaced Valerie with Dreama, though at least here it was different, as she's a witch too. Season four also replaced Libby, the former Trope Namer for Alpha Bitch, with Brad as Sabrina's school nemesis.
Ashley's ultimate demise in Sanctuary was particularly predictable because in the two episodes preceding it, they were already gearing up her replacement.
Oddly played on Saved by the Bell. After losing Jesse and Kelly the producers introduced biker chick Tori who picked up Kelly's role as Zach's love interest. That still left a gap though, so rather than introduce new characters they transferred Jesse's brains and Kelly's popularity to Lisa who overnight leapt from average intelligence and popularity to straight A-student and homecoming queen. More so on Saved by the Bell: The New Class, most blatantly in their first season. The new youngsters were virtual carbon copies of their old-class counterparts: Scott for Zack (even breaking the Fourth Wall in the same way), Weasel for Screech, Tommy D for Slater, Linday for Kelly, and Megan for Lisa and Jessie (due to her being Weasel's unrequited crush, as well as the smart one in the group).
The character of Laverne was killed off, due to the writers being under the impression the 6th season would be the last. It wasn't. Cue Nurse Shirley, who is played by the same actress that played Laverne! This is lampshaded when JD nicknames her "Laverneagain." The hospital's fake website uses the exact same picture for both nurses' profiles. It's actually a subversion, since what little personality the writers had a chance to give to her dialogue, and a good deal of the acting Aloma Wright did, was meant to create the impression of an anti-Laverne. Laverne and Shirley?
For the last season, the main character is JD and Elliot combined (narrator, daydreaming delusions, blonde, crazy, likes horses, bullied by Dr. Cox...) and Denise is also given some more obvious JD traits after he leaves. Denise and Drew sort of become the new Jordan and Dr. Cox.
Silent Witness replaced Harry (handsome, cocky, quick-witted, plenty of UST with Nikki) with Jack Hodgson (handsome, cocky, quick-witted, plenty of UST with Nikki.) Jack did have the differentiation of being Irish and having his sideline as a cage-fighter worked into the storyline.
Silicon Valley: After the actor who played Peter Gregory died, his character was killed in the show and his job was filled by Laurie, a new character who is also a brilliant tech investor with No Social Skills.
The German police drama Siska did this when they replaced the eponymous lead character with his never-before-mentioned brother after he was killed off.
Sliders was rife with substituting toward the end, though most weren't very similar to those they replaced. However, Quinn got substituted when actor Jerry O'Connell left, by way of The Nth Doctor by being "fused" with 'Mallory' (his non-identical counterpart from a parallel universe), at the same time Colin wasPut on a Bus. But with a different personality and face, Quinn Mallory's substitute isn't the other Quinn Mallory. Hot Scientist Diana Davis takes his role as the scientific brains on the team. A certain segment of the fanbase believes that Arturo was substituted byhis own alternate. The episode that this happens in allows for that interpretation as Arturo's villainous duplicate tries to replace him so he can escape his own world and just before they slide they are having a classic "which is the real one?" battle, and after the slide, the Arturo who was left behind gives a quiet, "Oh, my God." Worse yet, Series creator Tracy Torme has tormented fans by saying that he knows which Arturo made the jump, but will never reveal it.
Tess came off as an example when she was first introduced, seeming like not much more than a Distaff Counterpart to the recently-departed Lex, but she pretty quickly gained her own personality and motivations. It's very likely that her status as a Suspiciously Similar Substitute is intentional in-universe, as she seems to hero-worship Lex and is likely emulating him as much as she can. In season ten, her similarities to Lex become even more reasonable when it's revealed that they're siblings.
Annie replaced Fi as the protagonist in the final season of So Weird. Like Fi, Annie had paranormal encounters that she posted on a website. The "twist" was that she was a singer.
The Sopranos killed off the character of Richie Aprile in the twelfth episode of the second season. In the second episode of the third season, Ralphie is introduced. Although you could never mistake them for each other, they occupy very similar places in the show's universe; he even ends up dating Janice.
One of the world's few substitute anticipations happened in the kids' series Space Cases. With Jewel Staite having Flash Forward (1996) hanging in the balance, her character, Catalina, was given an "imaginary friend" named Suzee, who was really a person living in Another Dimension that Catalina could communicate with. When the other series required Ms. Staite's services, a little Applied Phlebotinum switched Suzee to the real world (as played by Rebecca Herbst) and Catalina to the "imaginary" world.
The Metal Heroes series Space Sheriff Gavan has Gavan's Bridge Bunny Mimi leave to see to her ill mother for the last 3rd or so of the series, and replaced with a character called Marin who was the exact same character minus the Love Interest part (since Mimi was only leaving for a short while so her and Gavan were still technically in a relationship). Unlike most examples, though, Marin was already an established character on the show as a Bridge Bunny to Gavan's Mission Control and was specifically called in to fill in for Mimi.
Charlie Crawford replaced Mike Flaherty as the Deputy Mayor on Spin City. The key difference was that Charlie was a Handsome Lech and Mike wasn't. Charlie Crawford was played by Charlie Sheen, who also played Charlie Harper in Two and a Half Men. Sheen ended up getting fired from the show due to his drug problems and for making derogatory remarks about the show's creator and executive producer. Harper was killed off and replaced by Walden Schmidt, played by Ashton Kutcher. Both characters are immature womanizers.
Jonas Quinn was sort of like Daniel Jackson... but from another planet! However, after Michael Shanks decided to return as a regular, Jonas Quinn was abruptly and permanently written out of the series at the beginning of the seventh season.
Despite being the Trope Namer for a while, Jonas Quinn wasn't even the best example of this trope on this show. Cam Mitchell, an Air Force colonel with a snarky sense of humor and a tendency to make pop culture references (like the actor Browder's character in Farscape) replaced Richard Dean Anderson's character, Jack O'Neill, when he started Commuting on a Bus to spend more time with his family. This somewhat falls under the "military role" exception but is more likely due to a desire to have a new leading man, particularly one with a built-in audience. In addition, the "military role" exception doesn't explain their sufficiently similar personalities; Mitchell hadn't Seen It All like O'Neill, had a lower rank, and lacks the Ancient gene, but other than that they could have delivered the same lines.
When Dr. Frasier was Killed Off for Real, a new doctor, Dr. Lam, came in to replace her in season 9. The replacement was not immediate and the character was not as well developed.
This trope received its Lampshade Hanging (along with about a hundred others) in "200," when an actor backs out from playing the lead in the Show Within a Show based on the SG team's adventures, leading to the quote on the main page. And at the end, we find out the "Colonel Danning" character from Wormhole X-Treme! was substituted. "Dr. Levant" is not indicated to have had a Suspiciously Similar Substitute when he left the show, but much like the realStargate SG-1, they may have resolved to never speak of it. And there's the humorous scene where other characters suggested that Cam was O'Neill's son from the time travel episode in Season 1.
One episode after the Prometheus was destroyed, we get a new one called the Odyssey, which bears a resemblance to Prometheus aside from having larger docking bays and the Asgard systems built into it instead of being tacked on after the fact.
Jewel Staite's Dr. Keller also replaced Dr. Beckett on Stargate Atlantis as the caring and sometimes out of his/her element doctor, despite having appeared on the series previously as a different character (as an alien with heavy prosthetics, but still).
The Goa'uld Tanith was abruptly killed off midway through series five due to scheduling conflicts, despite his somewhat important role as a herald to the ominous Anubis. For the "Summit"/"Last Stand" two-parter when Anubis finally announced himself to the other System Lords, he was suddenly being represented by Zipacna, a Goa'uld from two seasons prior who had until then seemed to be a one-off character.
The series used this with Star Trek: Voyager and Star Trek: Enterprise — though for different reasons. ENT was intentionally a merging of the holy trinity of Kirk, Spock, and Bones with the "new generation" Trek tropes. Conversely, VOY germinated as an unaired eighth season of TNG before being retooled into a spinoff.
The characters of TOS were based on the characters originally conceived for the rejected pilot, with Pike becoming Kirk, Boyce becoming Bones, Smith becoming Rand, etc.. This practice is extremely commonplace when a Pilot turns into a green-lighted series. Similarly, the characters of TNG were based on the characters of the abandoned "Star Trek: Phase II" series: Will Decker became the similarly-named Will Riker; Decker's old flame, the empathic Deltan Ilia, became Riker's old flame, the empathic Betazed Troi; and Xon, the Vulcan struggling to understand humanity, became Data, the android struggling to understand humanity. A writer's strike proved to be nothing more than a minor inconvenience for TNG: they just dusted off some old "Phase II" scripts and went to work (though only one script ended up being used for the strike-shortened second season; another was pushed back to season four).
Following the success of TNG, a pattern began to emerge in the crew's makeup. There will always be an overeager, wet behind the ears kid for the young audience to relate to (see Wesley Crusher, Jake Sisko, Naomi Wildman); an inexperienced recruit (Dr. Bashir, Harry Kim, Travis Mayweather); a comic relief hustler with gross alien habits (see Quark, Neelix, and Dr. Phlox). Sometimes the characters were just obvious stand-ins for a more famous predecessor: Tuvok, the gruff, socially-awkward Vulcan security officer, was substituted for Worf, the gruff, socially awkward Klingon security officer for instance.
For one season of Star Trek: The Next Generation, Dr. Kate Pulaski (played by Diana Muldaur, who'd appeared twice as different characters in the Original Series) replaced Dr. Beverly Crusher as ship's doctor. Pulaski was doubly a Suspiciously Similar Substitute since her abrasive tics were explicitly based on Bones McCoy.
In a case falling halfway between Suspiciously Similar Substitute and The Nth Doctor, Star Trek: Deep Space Nine replaced Jadzia Dax with Ezri Dax in the final season: different hosts, same symbiote, and a Trill's personality is a blend of the host and symbiote.
In the early production of Star Trek: Deep Space Nine, Kira Nerys was actually a replacement character for Ro Laren, because the actress that played Ro in Star Trek: The Next Generation declined the offer to appear in Deep Space Nine. The trope was mostly averted as Kira was developed into a very different character than Ro; most notably, Kira wasn't a Starfleet officer and as such related to those who were differently, especially in the beginning.
The exact same thing happened in the early production of Star Trek: Voyager: B'Elanna Torres was also a replacement character for Ro Laren because Michelle Forbes again refused to commit to a seven-year show.
The character Tom Paris from Voyager was originally slated to be Nicolas Locarno (a single-episode character from TNG) but the producers did not want to get into a situation where they could have been forced to pay royalties to the original writer of the TNG episode, so they changed the name of the character. They then turned this trope Up to Eleven as both characters were played by the same actor, and they have a nearly identical backstory. Some producers have mentioned that they also believed that Nicolas Locarno was irredeemable. They wanted a character that was a little rough around the edges, but ultimately redeemable. However, this may just be an official reason given to the press to cover the fact that they didn't want to pay royalties.
Taurik, a Vulcan Ensign who appeared in a single episode of Star Trek: The Next Generation, became a recurring crew member in Voyager, where he was called Vorik, for the same reason that Locarno became Paris and T'Pau became T'Pol. Jeri Taylor, a producer on Voyager and the mother of the actor (Alexander Enberg) who played Taurik and Vorik, once quipped that the rhymedly named Vulcan Ensigns were identical twin brothers. This is stated as fact in the video game Star Trek Starship Creator.
T'Pol of Star Trek: Enterprise was originally written to be T'Pau, a Vulcan priestess who appeared in the Original Series. But since it was thought at the time that reusing a character would force them to pay royalties to the writer who created the original T'Pau, the character was changed. T'Pau did appear in the fourth season during a story arc on Vulcan. It was some years later that a judge in California ruled that such a reuse would not force a producer to pay royalties to the original writer.
Step by Step replaced Cody (upon actor Sasha Mitchell's run-in with the law) with Bronson Pinchot's character, who, despite being French, was essentially the wacky roommate Cody was in every way. They also had the character of Flash, so nicknamed because he was an adult with the hyperactivity of a four-year-old. He was essentially another Cody given a justification.
Fans have pointed out that whenever Sam or Dean get separated from each-other for a length of time, either brother tends to latch onto substitutes with a similarity to the other. For Dean it's been Cass, a siren and most prominently Benny; for Sam it's been Ruby and other female partners with a vague resemblance to Dean.
Ruby's character could be summed up as "Meg plus HeelFace Turn," which caused some speculation that she really was Meg in disguise, conning the boys for some nefarious purpose. It was possibly lampshaded in "Sympathy for the Devil" when Dean confuses Meg for Ruby despite having personally killed the latter only one episode ago. Revealed in the official third season companion guide to be deliberate when Eric Kripke even explained that the writers were trying to recreate the magic they made with Meg when they invented Ruby. Ironically, Meg ended up ripping off of Ruby upon her return to the series, bringing things full-circle.
The blonde, morally-grey, sarcastic, mischievous angel Balthazar was very, very similar to the blonde, morally-grey, sarcastic, mischievous dead angel Gabriel (except taller, blonder, and with a hot British accent). Balthazar was eventually also killed, and was not immediately replaced, but Gabriel was brought back several seasons later.
Some fans commented at the time that the character "Frank" seemed like an unnecessary replacement for Bobby, who was taken away from the leads to supposedly "strip the show back down to just the brothers." However, Frank only outlasted Bobby by a handful of episodes.
When he was first introduced, many fans feared that Benny would replace Castiel as Dean's gravel-voiced, coat-wearing, non-human BFF. It was revealed that, in fact, Benny helped Dean find Castiel in Purgatory, and the two were reluctant allies while trying to escape. Castiel, of course, outlasted Benny by seven seasons.
When the characters found an alternate universe containing many of the same people as their own universe, the alternate versions of several characters who had died at some point in the series were brought over to the main universe, including Bobby Singer and Charlie Bradbury. It became clear, however, that because these people were from a universe where they'd been fighting for their lives during an ongoing apocalypse for years, their personalities were not entirely the same as Sam and Dean's friends from their own universe. Some fans felt it was a cheap way to "bring back" these characters without actually bringing back the original characters they loved.
Jack Kline is ultimately very similar to Jesse, a single-episode character in Season 5 who has proven to be an Ensemble Dark Horse among the fandom but hasn't gotten a reappearance since. Both Jack and Jesse are Half-Human Hybrids who are extremely powerful, both are thought to be evil by nature, both are ultimately an Anti-Antichrist, and both hold a significant connection to Lucifer (Jesse is a half-demon who was prophesized to become the biblical Antichrist, whereas Jack is Lucifer's biological half-archangel son).
While all Princes of Hell besides Azazel were said to have lost faith in Lucifer and Dagon was expressly the only Prince who had an interest in Jack in Season 12, Asmodeus is introduced the following season wanting to serve Lucifer and to locate and use Jack, replacing Dagon's role in the narrative after she was Killed Off for Real.
Much like Charlie, Alice in "The Scorpion and the Frog" is a quirky girl of slim build with specialized skills who helps the boys pull a caper.
Deliberately invoked by Kipling who intentionally plays himself up as another "flouncy" Crowley-like character in the Season 14 premiere. When called out on it though he admits that it doesn't suit him and drops the act.
Inverted in Season 15, when Jack dies and his body is almost immediately possessed by a demon, Belphegor. Belphegor, while played by the same actor, could not be more different from Jack in terms of personality; even his voice sounds different. But the main characters are forced to work with him for several episodes to get out of their situation, despite the fact that every time they look at him they see their dead son. He is clearly not meant as a "replacement" for Jack in the show, but they must let him take Jack's place in their lives, at least temporarily.
Cora is this for Erica, the only female werewolf in Derek's pack. From being the one seen trapped in the vault with Boyd (when many wondered if Gage Golightly may have made a surprise return) to her relationship with Stiles, which is similarly part snarky and part flirtatious, she's just too similar to Erica for viewers to overlook. Since Adelaide Kane (the actress playing as Cora) eventually left the show, she was in turn replaced by Malia Tate.
After Allison's death, Kira appears to be her substitute as Scott's love interest.
Taken Up to Eleven in Season 4, which saw the addition of Mason, a gay male high school freshman who's a POC, star athlete on the lacrosse team, best friends with blond jock Liam, and isn't aware of the supernatural events going on around him. Sounds great until you realize that that almost word for word describes Danny Mahealani, who was mysteriously cut from Season 4, has had minimal Character Development since Jackson's departure two seasons ago and was an Ensemble Dark Horse amongst the fandom and casual viewers.
That '70s Show replaced Eric and Kelso with Randy, who had similar personality traits of both other characters.
In The Thick of It series three has a new Minister For Social Affairs — Nicola Murray replacing Hugh Abbot. Her only points of difference with her predecessor are that she's a woman and that she's not best friends with her main ministerial advisor. This is entirely justified, as the premise of the show is that all politicians are the same.
On The Thin Blue Line Kray was replaced with Boyle for series two. The general opinion is that Boyle was a lot funnier.
The Tick (2001) suffered from a number of poor copies meant to be substitutes when Fox failed to get the rights for any characters besides The Tick and Arthur. But given that it was Fox, no one was really surprised as the show's days were numbered from day one. Though, to give credit where credit is due, Bat Manuel is one of the funniest television characters ever. Even better the actor who played Bat Manuel in the live-action version of The Tick played the Mayor in the Batman movie The Dark Knight.
Played with on Tremors: The Series when Michael Gross was unavailable for shooting. The female scientist who appeared in the episode was given a personality Suspiciously Similar to Gross's Burt Gummer, a similarity which was lampshaded by the other characters, although she didn't perform his usual in-universe functions of shooting or blowing up monsters.
Leonard Rossiter's final role on UK television was as a supermarket manager in the dreadful sitcom Tripper's Day. After his death, he was replaced by Bruce Forsyth and the show was renamed Slinger's Day. This was (not surprisingly, given the new protagonist) even worse than the original but was somehow renewed for a second (six-episode) season and crossed the Atlantic to become Check It Out.
On Two and a Half Men, Clark Duke looks so much like a younger Angus T. Jones that a casual observer might think they are brothers. In fact, in one episode everyone, even Alan, confuses Walden's new intern Barry for Jake.
Upstairs Downstairs replaced Elizabeth, daughter of Sir Richard and Lady Marjorie Bellamy, with Georgina, the daughter of a couple killed in the Titanic disaster alongside Lady Marjorie. The changeover wasn't immediate, and demure, idealistic Elizabeth had a very different character to the louche Georgina, but Georgina filled the same role, so it may count. Lady Marjorie's role went through two changes as well, with Hazel and then Virginia Bellamy taking over the position of mistress of the house. Downstairs, after Emily's suicide, the show also went through a handful of identikit kitchenmaids before settling on the hapless Ruby.
In Welcome Back, Kotter, as John Travolta — who played Vinnie Barbarino — became a celebrity, he left the show (returning every so often as a "special guest star"). His "replacement" was Steven Shortridge as Beau, a transfer student from New Orleans.
Will Bailey seems to have begun as one for Sam Seaborn (right down to several "passing the torch" incidents in which Sam encouraged Toby to accept Will's help with the Inauguration speech, Will was semi-formally inducted into Sam's old position, etc.), but the writing of the show shifted after Aaron Sorkin's departure, and within a year Will's character had shifted jobs into the Vice-President's office and was portrayed more as a cynical political operative than as an idealist. Joshua Malina (Will) has even described himself as a worse-looking, less-expensive Rob Lowe (Sam). Which you have to admit has a grain of truth to it.
Joe Quincy (Matthew Perry), who was hired to fill a position opened by Ainsley Hayes (Emily Procter), a "blonde, leggy Republican." Yeah, he was a Republican too. Josh doesn't like that the similarities end there.
Josh: If you're a Republican, you damn well better look like Ainsley Hayes! Donna: He does! [Joe and Josh stare] Donna: I mean... he will to other people!
The show seems to be unable to hang on to the actor playing the White House Counsel, and so the feeling of similarity is probably due to the fact that the dialogue the new guy is sprouting was actually written for the previous guy. The scene that introduces Counsel Oliver Babish (the one with the oversized gavel and dictaphone) was pretty obviously written with Lionel Tribbey (his predecessor) in mind.
White Collar introduced FBI agent Diana Barrigan in the pilot, but when the actress had other commitments, she was replaced without explanation by the character Lauren Cruz. (Who was subsequently re-replaced without explanation by Barrigan in season 2.) Diana took a job in Washington, DC because it's where her girlfriend was from and decided to come back to New York. Lauren left with no explanation.
The UK kids' show Why Dont You (short for the surprising suggestion "Why don't you just switch off your television set and go out and do something less boring instead?") is another example, but it had one notable exception in its later years: Ben, the Welsh Mad Scientist, was evidently considered un-substitutable, so he continued past the typical age, eventually playing a Holly-style computer program based on the original Ben so that the disparity between his age and the rest of the cast wasn't an issue.
In the Australian teen series Wicked Science, the girl in Toby's group, Dina, was replaced by Toby's cousin Sasha in Season 2.
The Wild House replaced Serena with her cousin Georgina, who was the same age and had the same personality traits; being boy-crazy and clashing often with Natalie. The main difference between them was that Georgina was supposed to be more rebellious and demanding, but this didn't really come across in any major way other than dress sense and an ongoing subplot where Georgina had various misadventures whilst learning to drive.
Reviews of The X Factor's new judges Kelly Rowland, Tulisa, and Gary Barlow recall up their respective predecessors, Dannii Minogue, Cheryl Cole, and Simon Cowell. Some reviewers even noted that Tulisa even physically resembled Cheryl in terms of looks and personality.
Agents Doggett and Reyes are an interesting case. When David Duchovny left, it was a Scully who'd by now Seen It All who played Agent Mulder for newcomer Doggett's Agent Scully. Of course, when she went away for a while, Doggett was more seasoned, and here comes a new partner for him in the form of Reyes...
Also the various informants, starting with Deep Throat, coming into X, and finishing with Marita Covarrubias.
One case was forced: "Travelers" and "Agua Mala" featured Arthur Dales, the first FBI agent to deal with X-Files. Dales' actor Darren McGavin suffered a stroke filming "The Unnatural", leading him to be replaced with M. Emmet Walsh playing his brother Arthur Dales, a former police officer (who lampshades his parents didn't have much creativity with names). To make it worse, both Dales were played in flashbacks by the same actor.