Often in cases of ensemble series, a character introduced into the series sometime later will be played by an actor who appeared on the show much earlier in a guest appearance as an entirely different character. In some cases, it could be because the cast and crew enjoyed working with the actor enough to create a new regular or recurring character to be able to work with him more regularly, but a lot of the time, there's no actual explanation behind it.
The use of the same actor for different characters is typically intended to go unnoticed or at least unremarked. For example, Ed Wasser played Shadow minion Morden in Babylon 5 but also appeared in the series pilot as a minor crew member named in the credits as Guerra. Since that series was so intricately plotted, fans wondered if the Shadows were influencing events as far back as the pilot. No, said series creator J. Michael Straczynski, they just liked the actor's work in the pilot and cast him in a recurring role.
Spin-off shows will often encounter this, as the producers find actors they like for the new show.
Occasionally, if a series or franchise runs long enough, the inversion may also occur: an actor who played a regular role leaves, then returns guest-starring as a different character.
Subtrope of You Look Familiar. Compare Ascended Extra and Early-Bird Cameo.
- This happens in universe in Galaxy Quest, where actor Guy Fleegman (protrayed by Sam Rockwell) goes from playing a nameless Red Shirt on the titular show to being recast as the Protector's Security Chief in the Galaxy Quest revival.
- DC Extended Universe:
- Samantha Win played one-shot minor villain Car-Vex in Man of Steel. She went on to play the Amazon Euboea in both Wonder Woman and Justice League, who has a tad more notable things to do.
- Patrick Wilson voiced the U.S. President in Batman v Superman: Dawn of Justice, then played Orm in Aquaman, who's also set to reappear in the Aquaman sequel.
- In Ernest Goes to Camp, Gailard Sartain plays Jake, one of the bumbling cooks at Kamp Kikakee. In subsequent Ernest movies (as well as the Hey Vern, it's Ernest! TV series, and a series of commercials produced by Carden-Cherry - the same advertising firm that created the original Ernest commercials) he plays Chuck, Ernest's loud-mouthed and Know-Nothing Know-It-All pal and neighbor, and "twin brother" of Bobby.
- Joe Don Baker played James Bond's CIA contact in both GoldenEye and Tomorrow Never Dies, after having played a villain in The Living Daylights.
- Marvel Cinematic Universe:
- Enver Gjokaj had a cameo in The Avengers as a NYPD cop. He was later cast as Daniel Sousa in the prequel series Agent Carter, with the producers joking that the cop is Sousa's Identical Grandson.
- Alfre Woodard cameoed in Captain America: Civil War as a mother to one of the casualties of Avengers: Age of Ultron. She was later cast as major antagonist Mariah Dillard in Luke Cage (2016).
- Laura Haddock played a woman asking Steve for an autograph in Captain America: The First Avenger before playing Meredith Quill in the Guardians of the Galaxy films. Similar to the Gjokaj example above, James Gunn joked that the woman was Peter Quill's grandmother.
- Peter Mensah had a minor role in The Incredible Hulk as a colleague of General Ross before playing Recurring Character Qovas in Agents of S.H.I.E.L.D..
- Gemma Chan had played supporting antagonist Minn-Erva in Captain Marvel (2019) before being cast as Sersi, a main character in Eternals (2021).
- In the Godzilla series, stunt performer Kenpachiro Satsuma was initially hired to portray the one-off monster Hedorah in Godzilla vs. Hedorah (1971), and later played the recurring monster Gigan in Godzilla vs. Gigan (1972) and Godzilla vs. Megalon (1973). He went on to become the regular actor for Godzilla himself after the original stunt performer Haruo Nakajima retired from the role, making his debut in the 1984 reboot The Return of Godzilla.
- Sesame Street. Michael Jeter made a couple of guest appearances on the show in the late 90s, including his own version of the classic song "Dance Myself to Sleep" before being cast as Mr. Noodle's Brother Mr. Noodle while Bill Irwin (Mr. Noodle) was busy filming How the Grinch Stole Christmas!.
- In the Finnish version of The Men from the Ministry both Heikki Nousiainen and Antti Pääkkönen had several minor roles in multiple episodes before being cast as Lennox-Brown and Sir Clive, respectively.
- In the Tsukipro series:
- Manabu Kurita (Tooru, You's brother, in Tsukista 6:Kurenai Enishi) as You in 9-10 and the first Machine Elements.
- Yuuki Hirai (Romeo in ROMEO in the Darkness) as Kai in 9-present. Noteworthy in that he was also announced for lead roles in Identity V and Kuro to Shiro, Movista's first two non-Tsukipro productions, within a month of being announced for Kai, all in about 3 months after Romeo.
- Kouhei Tanaka (Shiki's brother Keito in SQS episode 5) as Reiji in Rock Down.
- In the Batman: Arkham Series, Matthew Mercer had a minor role in Batman: Arkham Origins as the villain Anarky for one of the side missions. The next game, Arkham Knight, had him take over as Tim Drake, one of the heroes and playable characters in the game.
- In the English dub of Bravely Default Michael Sinterniklaas provided the voice of Jackal, one of the bosses required to get one of the job classes for the game. For the game's sequel, Bravely Second, he portrayed the main protagonist, Yew.
- Jess Harnell, the current voice of Crash Bandicoot, had previously voiced Lo-Lo the Air Elemental in Crash Bandicoot: The Wrath of Cortex prior to becoming Crash.
- In The Last of Us, Laura Bailey is credited under 'Additional Voices'. Her voice can be heard as a reporter during the prologue and later as one of the FEDRA agents who catch Joel outside the wall. In the sequel, she plays Abby, one of the main characters.
- Command & Conquer: Subverted in the first two games Tiberian Dawn and Red Alert 1, both of which prominently feature Joseph D. Kucan, the first as Kane, the leader of the mysterious terrorists the Brotherhood of Nod and the second as an advisor to Joseph Stalin with the same goatee and (non-)haircut (given the cheap nature of the cutscenes, it doesn't look out of place to have the same actor in different roles). Then at the end of the Soviet campaign, it's revealed that no, that is Kane.
- The Nostalgia Critic: Tamara Chambers made her first appearance playing Anne Hathaway in the Catwoman (2004) review. She was Rachel Tietz's roommate at the time. When Rachel moved to California to pursue more acting work, Tamara took over Rachel's role as the female lead of the show.
- Avatar: The Last Airbender: Before voicing main character Toph, Jessie Flower voiced Meng from "The Fortuneteller".
- DC Animated Universe:
- On Batman: The Animated Series, before playing the Joker, Mark Hamill played the role of the Corrupt Corporate Executive that was responsible for Victor Fries's accident. This example crosses over with The Other Marty, as Joker had already had voice work recorded by Tim Curry, but it had to be replaced because doing so hurt his throat.
- Ron Perlman, who voices Clayface, also voiced a random thug (called "Driller") in the episode "P.O.V."
- Carl Lumbly had a couple of guest spots in Superman: The Animated Series and voiced Stalker on Batman Beyond before voicing the Martian Manhunter in Justice League.
- Dana Delany provided the voice of Bruce Wayne's love interest Andrea Beaumont in Batman: Mask of the Phantasm before going on to do the voice of Lois Lane for Superman: The Animated Series and Justice League.
- Sherman Howard voiced the Perserver and Steppenwolf in Superman: The Animated Series before being cast as Derek Powers in Batman Beyond.
- Michael Rosenbaum provided the voice of Ghoul for the film Batman Beyond: Return of the Joker, and Terminal in Beyond proper before later getting cast as The Flash for Justice League.
- The opening of Batman Beyond's first episode "Rebirth" saw C.C.H. Pounder as a reporter — years before Justice League Unlimited cast her as Amanda Waller.
- The JLU episode "Dark Heart" had Michael Beach as the male rock climber at the start and one of the soldiers before he was cast as Mister Terrific and Black Manta expy Devil Ray in the final season.
- In the first season of DuckTales (1987), Hamilton Camp voiced a few minor characters before voicing Gizmoduck in season two.
- In season 1 of Elena of Avalor, Grey DeLisle Griffin voices Dr. Mendoza. In late season 2, she's cast as Ash Delgado, who takes over as the main villain.
- The Loud House:
- Lincoln's first regular voice actor, Grant Palmer, would later voice Grant, an employee at the Burping Burger, after he hit puberty.
- Tex Hammond, son of series regular Grey Griffin, initially voiced minor character Lance before becoming Lincoln's third regular voice actor. Hammond's successor, Asher Bishop, also initially voiced Simon Sharp before getting cast as Lincoln.
- In Rugrats, Tara Strong voiced Timmy McNulty, a Jerkass neighbor of the babies around Angelica's age, before going on to voice Tommy's brother Dil. Likewise, Nancy Cartwright voiced Prudence the Junk Food Kid in "Showdown at Teeter-Totter Gulch" before becoming Chuckie's voice actress following Christine Cavanaugh's retirement from voice acting.
- On Scooby-Doo! Mystery Incorporated:
- Kate Higgins voiced some minor characters in Season 1 (namely Principal Quinlan in one episode) before being cast as Mayor Janet Nettles in Season 2.
- Tia Carrere played Amy in "The Siren's Song" before being cast as adult Judy in Season 2.
- The Simpsons: In the Canadian French dub, Alain Zouvi voiced several one-shot characters such as Brad Goodman, Hank Scorpio, and Frank Grimes. Afterward, ever since "Lisa the Skeptic", he became the official voice actor for both Smithers and Apu, replacing the late Jean-Louis Millette in both roles.
- In Sofia the First, Megan Hilty played Princess Charlotte in season 3's "Beauty Is The Beast" before being cast as Prisma, the main antagonist in the Mystic Isles story arc for season 4. Likewise, Andrew Rannells, who voiced Morris in that episode, would voice Skye, Sofia's flying horse companion in the titular isles, another regular in season 4. There's also Fiona Bishop, who voiced Ruby in the pilot movie "Once Upon A Princess", voicing Princess Zooey, and Buttercup twins Meg and Peg.
- SpongeBob SquarePants: In the Spanish dub, Luis Miguel Perez did additional voices and dubbed the songs, "Doing the Sponge" and "Loop De Loop", before replacing Oscar Zuloaga as Plankton.
- Star Wars Resistance:
- Josh Brener, a friend of Rebels main cast member Tiya Sircar (Sabine), was the voice of Senator Mon Mothma's attaché, Erskin Semaj, before later playing a main role as Neeku Vozo.
- Gary Anthony Williams played One-Shot Character Separatist General Riff Tamson on The Clone Wars before later playing recurring character Kragan Gorr.
- In the Latin American dub of Steven Universe, Valentina Toro voiced Alexandrite in her first appearance before later going on to voice Jasper. Ironically, her sister Antonia would voice Alexandrite in her second appearance. Similarly, before she became the Spanish voice actress for Ruby, Judith Noguera voiced minor (as in, she doesn't even have her own voice actress in the original language) recurring character Jane.