'''Basic Trope''': A character is killed but the actor returns as his hitherto unseen (usually twin) sibling.
* '''Straight''': Alex is KilledOffForReal. In the next episode, Alex's long-lost twin brother Bob is introduced and continues to play pretty much the same role. Bob was not shown or mentioned in any previous episodes.
* '''Exaggerated''':
** After an EverybodyDiesEnding, all killed characters are revealed to have long-lost twin siblings. The cast remains exactly the same.
** The twin dies, and it turns out there were triplets. Then the triplet dies and it turns out there are a whole ton of backup siblings.
** Flashbacks in earlier episodes explicitly show that Alex grew up with only his parents. Despite this, Alex's brother Bob is abruptly introduced.
* '''Downplayed''':
** Alex is KilledOffForReal. In the next episode, Alex's long-lost twin brother Bob is introduced and [[DemotedToExtra makes a few guest appearances]] from then on.
** Bob [[EarlyBirdCameo appears in a few episodes]] before [[AscendedExtra replacing Alex as a main character]].
** Bob is just a regular sibling of Alex (or perhaps something even further out, such as a half-sibling or even a cousin), and though he shares some looks, quirks, and personality traits with Alex, he also has quite a few of his own.
* '''Justified''': Alex and Bob were long estranged, but the other characters already knew about Bob. When Alex died, they specifically sought Bob out and convinced him to take over Alex's duties.
* '''Inverted''':
** Alex [[BackFromTheDead resurrects]] his dead twin brother Bob, then takes a LongBusTrip. More so if Alex returns a few seasons later and rekills Bob.
** Alex died before the events of the show, and is only seen in flashbacks.
* '''Gender-Inverted''': Alex dies and is replaced by his HalfIdenticalTwin ''sister'', Roberta, as a favor to the [[CrosscastRole actress]] playing his part.
* '''Subverted''':
** Bob is actually an impostor who took on Alex's appearance to infiltrate the circle of his friends.
** It turns out that Alex has faked his death, and that Bob is actually him.
** Bob shows up... And, aside from looks, is ''nothing'' like Alex.
** Shortly after his introduction, Bob undergoes a rapid bit of DivergentCharacterEvolution, and soon he is nothing like Alex.
** Alex [[NoOneCouldSurviveThat seemingly dies]] but returns after Bob jumps in, kicking off a heated argument on who is the real Alex now.
** Alex is resurrected from the dead; it turns out that his "death" was nothing more than a publicity stunt.
* '''Double Subverted''':
** After getting to know Alex's friends, the impostor Bob decides to [[BecomingTheMask become the mask]].
** It turns out that Alex was Bob all along, got tired of acting like his twin, faked his death, and reappeared as himself.
** Bob is hypnotized to act like Alex.
** "Alex" was Emperor Evulz in disguise.
** Claire later dies and is replaced by her sister Diane.
* '''Parodied''': Alex has vats of clones ready to replace him in case he dies, and they are all individually named in order to resemble siblings.
* '''Zig Zagged''': ????
* '''Averted''':
** Alex does not have a sibling to replace him.
** EverybodyLives
* '''Enforced''': "But he signed a contract with us for the entire season! You can't just kill him off like that! Find a way to put him back in!"
* '''Lampshaded''': "Ah, you must be Alex's twin brother. Nice to meet you. I guess there's no need to tell you that HeDidntMakeIt."
* '''Invoked''': Bob decides to replace Alex as part of TheTeam.
* '''Exploited''': ???
* '''Defied''': Hearing about Alex's death, Bob blows town to avoid associating with whatever business Alex was in. [[PutOnABus He is never seen or mentioned again.]]
* '''Discussed''':
** "HesDeadJim." "Check his family records for any unaccounted-for twin siblings."
** "Sir, I know what you are thinking but if Alex ''did'' have a twin, don't you think he'd tell us?"
* '''Conversed''': "Why did they bother killing Alex if they were just going to bring Bob in to replace him?" "Alex was a main character. Duh! At least they didn't pull out a DisneyDeath."
* '''Implied''': Alex dies, and a character resembling him starts appearing in his place. The others simply refer to him as "Not Alex".
* '''Deconstructed''':
** Alex's friends find Bob whose personality is nothing like Alex's, and an attempt to substitute him with Bob [[DrivenToSuicide ends badly]].
** Alex died in a way that was noble and deeply affecting, so the audience views the attempt to "bring him back" in the form of Bob as a cheap trick which sullies their memory of the character.
* '''Reconstructed''':
** Alex's friends find Bob whose personality is nothing like Alex's but he learns to do what Alex did in the group and they learn to like him for what he is.
** Alex was a popular character, so most fans think it was a mistake to kill him off. As a result, they are thankful that Bob was introduced to fill Alex's role.
* '''Played For Laughs''': Though physically identical, Bob is nothing like Alex, forcing the main cast to go to ridiculous lengths to cover for his mistakes and/or explain his changed personality to those who knew Alex well.
* '''Played For Drama''':
** Alex's girlfriend cannot accept Bob but is forced to appear together with him to maintain the secret of Alex's death.
** Bob is [[AngstySurvivingTwin deeply effected by brother's death]], and he's in town to get some closure, bringing with him all the {{angst}} and/or [[ItsPersonal bloodshed]] he can carry.
** Bob, who is TheUnfavorite, is groomed by his AbusiveParents to become a [[ReplacementGoldfish replacement]] for his dead twin brother.
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