Convenient Replacement Character
aka: Welcome To The Liberator
This is the uncanny habit of a new character arriving conveniently in time to replace an outgoing one, generally in the same episode. Sometimes there is a certain logic to this, as in the case of Starfleet officers being succeeded by another of the same rank. Other times, it's just to make up the numbers, such as in Blake's 7, when the new character is always the same gender as the outgoing one. A frequent vehicle-of-delivery for the Suspiciously Similar Substitute. When a Tabletop Game player does this in an especially cheesy fashion, it's a symptom of Complacent Gaming Syndrome. Compare Backup Twin when it's really convenient.
- With each new generation of Pokémon (besides generation II), Ash is accompanied by a different female companion. Misty (The Original Series) is succeeded by May (Pokemon Advanced Generation), then Dawn (Pokemon Diamond and Pearl), then Iris (Best Wishes), then Serena (Pokemon X and Y). Starting with Best Wishes, Ash's male companion is also different and largely serves in the same roles (being a gym leader, The Lancer and a Team Chef.)
- Kind of in the same vein as the Final Fantasy example below, in the sci-fi novel Wyrm, the main characters are very much deep into the viral MUD central to the plot when one of the characters they're playing dies. Luckily, that player just happened to have a back-up character that had been following close behind them the whole time without them noticing.
- In Blakes Seven Jenna is replaced by Dayna, Blake is replaced by Tarrant, and Cally is replaced by Soolin. This series was once in fact the Trope Namer: Welcome to the Liberator, in honour of the ship featured on the show. Which was replaced by the Scorpio
- In Frontline, each season features a new executive producer, all of whom are equally amoral but manipulate people in slightly different ways.
- In Star Trek: Voyager, Seven of Nine is introduced in the season 4 premiere (carrying on from the season 3 finale's cliffhanger). Kes leaves the show in episode 2 of Season 4 (after it's established that Seven is staying).
- Averted by "The Best of Both Worlds", the Star Trek: The Next Generation season 3/4 two-parter. It looks like Shelby will be taking Riker's place as first officer, first when he's given his last shot at a command assignment, then when Riker assumes command of the Enterprise after Picard's abduction, she actually does become his first officer. Of course, Picard is saved, the ship Riker was offered command of is destroyed, and Shelby moves on to something outside the focus of the show.
- Law & Order: Special Victims Unit: In the first episode of the second season, Ice-T's character shows up, having been reassigned to SVU. Monique Jeffries, Michelle Hurd's outgoing character, comments, "You're here for my job."
- Doyle makes a Heroic Sacrifice to save the title character of Angel. Wesley arrives in town in the next episode.
- MASH... Where to begin? Trapper for BJ. Henry for Potter. Frank for Winchester. Klinger takes a more central role after Radar leaves too. Justified, as these are military jobs that need to be filled.
- The Joel-to-Mike swap on Mystery Science Theater 3000 was a justified example: Mike's first episode is Joel's last because Mike helps Joel to escape. Upon discovering that Joel is gone and they need another test subject to continue their experiments, the Mads force Mike to take Joel's place.
- NCIS: After Agent Caitlin Todd is murdered in the season 2 finale, Ziva David appears in the two-part opening episode of season 3 - which still features Kate, after a fashion (she is appearing as other character's hallucinations of her) - but isn't revealled to be a regular until an episode or two later. Actually subverted when Ziva leaves: She leaves the cast in the second episode of Season 11, but her replacement, Ellie Bishop, doesn't arrive until mid-November.
- Doctor Who traditionally did this with great frequency, although there was an aversion in the last few Tenth Doctor stories. Possibly justified on the grounds that the Doctor gets lonely without a companion, or foresees one leaving, and starts actively looking for a new one.
- Stargate SG-1: In the Daniel Jackson to Jonas Quinn swap, Jonas is introduced in "Meridian", which is the same episode Daniel gets sent off to a higher plane. And then, when Daniel comes back, that fits this too; Daniel's back, so Jonas skedaddles back home same episode.
- In Minder, Arthur's nephew Ray arrives looking for a job in the same episode (the season opener) that Arthur learns Terry has emigrated to Australia.
- A few of the early Super Sentai and Power Rangers seasons had this happened whenever a retiring cast member needed to be replaced:
- The two replacements in Battle Fever J. Maria Nagisa shows up just when Diane Martin (Miss America) gets injured, whereas Makoto Jin happens to befriend Team Battle Fever just before Kensaku Shiraishi (Battle Cossack) is killed.
- Taiyou Sentai Sun Vulcan has The Hero Ryuusuke Oowashi (Vul Eagle)'s classmate, Takayuki Hiba, arrive after a hard battle. He's given a tour of the heroes' new base, and then their commander informs Oowashi that he has to go pilot a space shuttle for NASA. Of course, Hiba turns out to be there to replace him as the leader of the team.
- We also have the second Yellow 4 in Choudenshi Bioman, though plot allows the replacement to arrive smoothly: the Biomen are the descendants of people who'd been showered with Bio Particles during the Edo period. There are, of course, more descendants than just those five, and the Biomen went and recruited one.
- Done regularly on Mighty Morphin' Power Rangers, seeing as only one of the original Rangers (Billy) stayed through the entire multi-season first story. Rocky, Adam, and Aisha befriended the Rangers before replacing Jason, Zack, and Trini in Season Two; and then Kat showed up for an arc before replacing Kimberly in Season Three.
- Power Rangers Turbo worked similarly; Justin was introduced in the same movie where Rocky got sidelined, and midseason it introduced four new characters before they became the replacement Turbo Rangers.
- Power Rangers Lost Galaxy was a partial aversion, as when Kendrix had to be written out due to Real Life Writes the Plot, both planned replacement characters were returning from the previous season Power Rangers in Space. It's only "partial" because both conveniently made their reappearances just as Kendrix left: Cassie was part of the Lost Galaxy/in Space crossover that led to Kendrix's death, and when the plans for Cassie to be a permanent cast member fell through Karone appeared and became the new Pink Ranger in the following episode.
- Two and a Half Men: Ashton shows up the same episode we found out Charlie was killed.
- Zigzagged on Farscape. Jool first appears in the same story where Zhaan leaves and takes over the position of ship's medical expert. However, Stark, who replaces Zhaan as the ship's mystic, had been an on-and-off guest star for a season prior to Zhaan's departure. Sikozu shows up to replace Jool as the annoyingly smart redhead chick a few episodes before Jool actually leaves. Averted with Noranti replacing Stark: there's a fairly large gap between Stark's departure and Noranti's introduction.
- In Bonanza, Will Cartwright was set up to be this for Adam Cartwright, but it was subverted when Will ended up leaving the show before Adam did.
- NewsRadio: After dealing with Bill's death in the first episode of the fifth season, his replacement, Max Louis, is introduced in the next episode.
- Last of the Summer Wine: It almost always happens when one of the members leaves the trio. Seymour is called out of retirement and leaves, and the long-gone Foggy returns to the village on the very next bus. Years later, Foggy is supposed to be temporarily out of town, and the lads hang out with Truly Truelove in his absence. However, Foggy's trip becomes permanent when he suddenly marries, and Truly simply carries on in his place.
- Rookie Blue: In Season 3, Sam's ex-bf, Detective Luke Callahan, returns to the division seemingly just in time for the current lead Detective Jerry Barber to get fatally stabbed within the next two episodes, leaving Luke to step up into Barber's old role.
- The Dukes of Hazzard: Bo and Duke leave to race cars, enter Suspiciously Similar Substitutes Coy and Vance. Bo and Luke return after the actors' contract dispute is settled, Coy and Vance leave town to aid a conveniently ill relative.
- When the actor who played Coach on Cheers died, they brought in Woody, not only to fill the job of tending bar, but also the job of The Ditz.
- Final Fantasy:
- Final Fantasy IV is practically the embodiment of this trope, as another party member will appear to fill in a gap left by a previous party member leaving, typically by Heroic Sacrifice.
- However, there are many instances where you don't have a full party in Final Fantasy IV. A better (but one-time) example is in Final Fantasy V, where you add Krile to your party literally the moment Galuf dies. The new character even gets all the old character's skills and equipment, making it feel like all you've really done is a sprite change (though she is a significantly different character).
- Final Fantasy II. You have your core 3 characters, and the fourth one dies, leaves, gets separated, dies, or dies. You don't get your final party until towards three quarter of the way through and that's your original party from the original cutscene. This is a nuisance seeing as the grinding system in this game depends on repeating one action repeatedly in order to become better with that action, so your fourth party members (with one exception) are all all but useless.
- Near the end of Dragon Age: Origins, sparing Loghain will lead to him replacing Alistair as your weapon-and-shield Warrior when Alistair storms off in a rage.
- Mass Effect 3 (and to a lesser extent, 2) uses a lot of them for characters that died in the previous games. For example, if Wrex died in the first game, he's replaced by his brother Wreav going forward. The replacement characters are usually worse when it comes to the outcomes of their story-arcs, though.
- You are the replacement astronaut in Rama after the mission commander's mysterious death.
- The Planet Express Ship crew in Futurama is explicitly this to a prior lost crew, and the Professor has convenient replacements in the same roles ready to step up when and if they die.