Characters in one series crossover
to another series. A technique used to help define a 'Verse
Anime and Manga
- This is what helped define the official Marvel and DC Universes back in the 50s and 60s.
- Obscure 1980s black-and-white comic Tales from the Aniverse featured a cat bounty hunter named Miss Chevious. Cartoonist Randy Zimmerman carried the character over into her own series, which runs in Flint Comix & Entertianment over 20 years later.
- The Buffy the Vampire Slayer Season 8 comic Time Of Your Life crosses over with Fray, which takes place in the future. Buffy meets Melaka Fray and finds out that Willow is still alive and wants her dead. In season 9, Willow tries to keep this from happening.
- Zany To The Max has at least one crossover per season. All the crossovers are in this style (either the Warners enter into the other series, or characters from the other series enter the Animaniacs world). Played for laughs in a parody of Monsters, Inc.
- Although the Discworld is technically one series, readers tend to group the books according to which recurring protagonist is the focus, and certain said protagonists cross over briefly into other books. (In particular, Pterry has noted that it's very hard to set a novel in Ankh-Morpork without the Watch taking an interest.)
- One What Could Have Been moment: at one point Pterry considered that the various powers attending the Low King's coronation in Thud! would include the King and Queen of Lancre. We'd know they were Verence and Magrat, but to Vimes they'd just be a couple of royals he was briefly introduced to.
- One of Bret Easton Ellis's signature techniques: Clay, the protagonist of Less Than Zero, is a minor character in The Rules of Attraction; Patrick Bateman, a minor character in The Rules of Attraction, is the protagonist of American Psycho, and so on.
- Agatha Christie does this a fair bit. For example, Inspector Japp of the Poirot series appears in the first Tommy and Tuppence book.
- Banjo Paterson's poem "The Man from Snowy River" namedrops the title character of another of his works, "Clancy of the Overflow." Clancy is also given a prominent role in the movie adaptation.
- And "Harrison, who made his pile when Pardon won the cup" is presumably the narrator and placer of the victorious bet in Paterson's "Pardon, the Son of Reprieve".
- Stephen King will often make brief references to characters and events from previous books, especially if those books took place in Castle Rock, Maine.
- The character Hoid appears in all of the works of Brandon Sanderson set in the Cosmere (Mistborn, Elantris, The Stormlight Archive and Warbreaker) to serve various roles, such as a begger or a storyteller.
- P. G. Wodehouse did this quite a bit, mostly by having characters in more than one series belong to the Drones Club or visit/make reference to Blandings Castle.
- S.M. Stirling's Nantucket series is confirmed to be connected to the author's Emberverse series.
- One of Thomas Disch's stories made a brief reference to the horrible fate of the main character in his story "The Roaches."
- Several characters from L. Frank Baum's lesser-known books made appearances in Oz, most notably Cap'n Bill and his ward Trot, and a boy named Button-Bright who had a talent for ending up precisely where he wanted to be despite getting lost along the way.
- Boston Public, Ally McBeal and The Practice had a crossover.
- Beverly Hills 90210 begat Melrose Place which begat Models Inc. Characters like Jake from Melrose Place appeared on 90210 before Melrose Place began. Later Melrose Place characters appeared on Models Inc. (Amanda Woodward's mother and half-brother ran Models Inc.). Later, some of the original 90210 cast members returned for the reboot of 90210 and some of the original cast of Melrose Place returned for the reboot of that show as well.
- Steve Urkel of Family Matters fame has appeared in both Full House and Step by Step.
- The characters in Angel and Buffy the Vampire Slayer inhabited the same universe and crossed-over regularly.
- Rumor has it, if Firefly had continued, at some point, the crew would have been passing a bar, one of the characters in a long black coat would have said, "Nothing ever bloody changes," before turning around to reveal himself as Spike.
- The Fray comics take place in the Buffyverse in the distant future, in which Buffy and the new slayers are long dead.
- Thanks to a whole mess of anarchy, same thing went between Hercules: The Legendary Journeys and Xena: Warrior Princess. Considering that Xena was originally a villain character from Hercules who ended up getting her own show, it was frankly inevitable.
- Characters from Cheers, including Norm, Cliff, Rebecca, and Frasier appeared on Wings, and later on the spin-off Frasier.
- Carla, Norm and Cliff were also in an episode of St. Elsewhere titled, amusingly enough, "Cheers". Carla has also appeared on the short lived Cheers spin-off The Tortellis which revolved around her ex-husband Nick, their brood of children and Nick's new wife Loretta most of which were recurring characters on Cheers.
- Dr. Roxanne Turner from St. Elsewhere showed up on an episode of Homicide: Life on the Street. Dr. Victor Ehrlich from St. Elsewhere appeared in the Homicide movie.
- Speaking of St. Elsewhere, related to this trope is the "Tommy Westphall Universe", a theory which posits that nearly 90% of all American television exists in a shared universe, which exists entirely inside the mind of Tommy Westphall, an autistic child character on St. Elsewhere who, in the series finale, is revealed to be looking into a snow globe and imagining the events of the television show. St. Elsewhere crossed over with many different shows, which themselves crossed over with, and spun off, many different shows, which themselves crossed over, etc, creating an interweaving "universe" than encompasses a good majority of American television.
- Richard Belzer has played Baltimore (later NY) PD detective John Munch on approximately a dozen different TV series.
- In addition to Belzer's example, Law & Order: SVU had Angie Harmon from the parent series consulting in the first series before they got their own, dedicated prosecutor. Whoever was playing the District Attorney in the parent series would also occasionally have an appearance.
- Characters from Stargate SG-1 and Stargate Atlantis regularly crossover.
- Several characters from SG-1 have also appeared on Stargate Universe more than once.
- McKay and Woolsey were both introduced as one-off antagonists in SG-1 before becoming regular characters on Stargate Atlantis. They both appeared in the Stargate Universe Season 2 episode "Seizure" to boot, making them the only Atlantis regulars bar Samantha Carter to appear in Universe.
- Characters from Friends and Mad About You have crossed over. Mostly it's been Phoebe and Ursula Buffet, identical twins both played by Lisa Kudrow. Kudrow originally appeared as Ursula on Mad About You, and when she was cast as Phoebe on Friends, the two characters were made into twins to explain their identical appearance.
- The Disney Channel did this with a triple crossover of some of their most popular shows, a mishmash called That's So Suite Life of Hannah Montana.
- They performed another hodgepodge later, with Wizards on Deck With Hannah Montana.
- Rare Panel Game example; before the final axing of its third part, Have I Got Buzzcocks All Over was an irregular Children in Need occurrence.
- Jack Harkness debuted in Doctor Who then got spun off into his own show, Torchwood. Similarly, Sarah Jane Smith originated on Doctor Who back in the '70s and then returned in the mid '00s before receiving her own spin-off, The Sarah Jane Adventures, taking K-9 along with her. Both of them returned for the 2-part fourth series finale of Doctor Who which also brought along two other characters from their own shows (Mr. Smith and Luke from SJA and Gwen and Ianto from Torchwood). Earlier Martha Jones had appeared on Torchwood for a story arc and later the Tenth Doctor visited Sarah Jane on SJA. Both characters then later reappeared for the Tenth Doctor's last story along with several other characters who had appeared throughout his tenure. The Eleventh Doctor appeared on SJA bringing along Jo Grant who was a companion to the Third Doctor just before Sarah Jane.
- In the Cold Open of the episode "Seminar" from The Office (US), Michael Scott runs into David Brent, his counterpart from the original British series. David appears again in the season 7 finale "Search Committee" as one of the people auditioning to replace Michael as manager.
- The character Director Leon Vance appears in both NCIS and, its spin-off, NCIS: Los Angeles, being that he is the director of the Naval Criminal Investigative Service in CBS's NCIS franchise.
- A very subtle version happens in the first season of NCIS when Bud Roberts from JAG appears as to consult on an old case.
- The character Penelope Garcia is the technical analyst in both Criminal Minds and its spin-off, Criminal Minds: Suspect Behavior.
- The second season finale of Cougar Town features appearances by Ted Buckland and Abed.
- The second season finale of Community also features a brief blink and you miss it cameo of two characters from Cougar Town. Also, Abed references his being an extra on Cougar Town in Community.
- Oddly enough, while some actors who have appeared in creator Bill Lawrence's earlier series Scrubs have also appeared in Cougar Town, Ted is the only character that appears in both shows, and the show Scrubs exists in that universe. He even noticed how weird it was that some of the characters in Cougar Town looked like people he knew.
- Naturally, the different iterations of Star Trek feature cameos from different characters, and share recurring nemeses like Q and The Borg. Worf is particularly notable for being a main character on both Star Trek: The Next Generation and Star Trek: Deep Space Nine. O'Brien also counts; he started out as a nameless extra in TNG's pilot episode, becoming one of the most recurring characters on the show before being pormoted to series regular on DSN.
- He's also an identically-named Identical Grandson of Colonel Worf in the last original Star Trek movie, allowing Worf to sorta be in three series.
- Every Star Trek series begins with a sendoff from someone from another (except the original, of course.) In Star Trek: The Next Generation McCoy visits the new Enterprise; in Star Trek: Deep Space Nine, Picard arrives at the station; in Voyager, we first meet Harry at Quark's bar. Of course, Star Trek: Enterprise is harder to do it with without Time Travel, but we do see a video of Zefram Cochrane, played by the same actor as in Star Trek: First Contact. And, Will Riker is actually in the holodeck playing out a historical recreation for the final episode (now considering this is a prequel series...)
- Even the films follow this: Star Trek: Generations includes several original cast members in the beginning and Kirk via basically time-travel passes the torch to Picard. While, in the more recent reboot, Spock travels back in time and explains the origin of the villain.
- Mr. Drucker appeared on both Green Acres and Petticoat Junction, as his grocery store was frequented by both show's characters. The two shows often had characters visit each other regularly in the early seasons.
- Bloom County cartoonist Berke Breathed carried over two characters from The Academia Waltz, a strip he did for his college's newspaper: Steve Dallas and Cutter John (then known as Saigon John).
- RPGs are well known for cameo characters making appearances in different games by the same developers, though these characters don't necessarily indicate that the games take place in the same universe, and are often a sort of internal Shout-Out.
- Cless and Arche from Tales of Phantasia appear in Tales of Destiny, as does Clemente from Tales of Destiny.
- Chelsea from Tales of Destiny appears in Tales of Eternia.
- Tales of Hearts raises this to a gameplay element; scattered through the game are artifacts that let you summon characters from every prevous Tales Series game to perform an attack for you in battle, from Arche to Ruca and Iria, and Caius and Rubia from the otherwise all but disowned Tales of the Tempest. As well as other characters from Bandai Namco games, like Gil, Klonoa, and KOS-MOS.
- Gilgamesh from Final Fantasy V makes appearances in other Final Fantasy games, such as 8, 9, and 12. And, retroactively, I and VI.
- Balthier from Final Fantasy XII and Luso from Final Fantasy Tactics A2 appear in the remake of Final Fantasy Tactics. Several FFXII characters also appear in A2, this time appearing to indicate that the two games do take place in the same universe. Same universe, same planet, even the same kingdom, for the most part. Ivalice, it's called. Vagrant Story's in there, too.
- Dissidia: Final Fantasy appears to indicate that all the FF games are part of the same "multiverse", if rather shakily.
- Bleu/Deis appears in several Breath of Fire games.
- Gabrielle Celeste and Ethereal Queen appear in all the Star Ocean and Valkyrie Profile games (made by tri-Ace). In addition, Lenneth and Freya from VP1 appear in Star Ocean 3; Puffy and Raddle the Traveler appear in all three Star Ocean games; Dirna Hamilton and Solon Solute from SO3 appear in VP2; Welch from SO3 appears in the remake of SO1.
- Many of Nippon Ichi's games feature crossovers, such as Etna and Priere.
- The Shin Megami Tensei series has included many crossovers, from the main character from Shin Megami Tensei if...... appearing in Persona and Persona 2, and more recently Raidou appearing in the rerelease of Shin Megami Tensei: Nocturne (in place of Dante) included with the special edition of Raidou Kuzunoha 2.
- A handful of overlapping characters is all that holds the Type-Moon multiverse together (the convoluted magic laws aside): Cool Old Guy Zelretch plays a large role in the backstory of Tsukihime and makes a cameo appearance in Fate/stay night. Cool Big Sis Touko Aozaki is a major character in Kara no Kyoukai, is mentioned briefly in Fate, and her sister Aoko appears in Tsukihime and is the protagonist of Mahou Tsukai no Yoru.
- While the older Ace Combat games were unambiguously set in the same Constructed World, their storylines were so self-contained that they could have just as well been taking place in parallel universes. However, a few overlapping characters linked the storylines together.
- The Monsta and Mighta enemies from Bubble Bobble also appeared in the earlier Taito game Chack'n Pop.
- Sam Durkin first appeared in The Shivah, he has since gotten a more expanded role in The Blackwell Series.
- Another Disney example — Kim Possible, Ron Stoppable, and Rufus the naked mole rat teamed up with Lilo in an episode of Lilo & Stitch: The Series.
- And again in another episode of the same show, this time with the titular character of American Dragon Jake Long and his two best friends teaming up with Lilo and Stitch.
- One episode of the TV version of Disney's Hercules involved a crossover with the cast of Aladdin.
- Many 1970's-era Hanna-Barbera adventure characters appeared in episodes of Scooby-Doo, and vice versa, including: Jeannie, Speed Buggy, Dynomutt, and Josie and the Pussycats.
- Similarly, a Space Ghost cliffhanger was resolved with the aid of the company's less-remembered Moby Dick interpretation.
- And then there's The Jetsons Meet The Flintstones. Hanna-Barbera loved this trope.
- Johnny Bravo also had a crossover episode with Scooby-Doo.
- DuckTales and Darkwing Duck have Launchpad McQuack in common as a main character, and Gizmo-Duck as a notable recurring one. Darkwing also saw the occasional cameo from Flintheart Glomgold, the Beagle Boys, and Magica De Spell.
- One episode of the Ace Ventura Animated Adaptation featured Stanley Ipkiss from the animated adaptation of The Mask.
- Animaniacs begat Pinky and the Brain, which became Pinky, Elmyra & the Brain with the inclusion of Elmyra from Tiny Toon Adventures.