Required Spinoff Crossover

""Hey, it's my old pals, the Simpsons! Why, what are the Simpsons doing in New Orleans?""

- Chief Wiggum, The Simpsons, "The Simpsons Spin-Off Showcase"

So, the Spin-Off has launched. All the requisite cast members have jumped ship, and you've got enough stylistic elements to draw at least a loose connection between the new series and its parent. But why stop there? Why not have recurring visits from members of the old series, who are just stopping in to say hi? Hell, why not have crossover events?

A Required Spinoff Crossover is what happens when a spun-off series decides to showcase its connection to the original series in its first season, often and with great vigor at times. Sometimes it will happen when a character from the first series stops by to follow up on a plot in the second series. Other times, there will be a full-on crossover, where both series get together to follow one plot. Either way, the show is going to remind you of its pedigree as loudly as it can. Note that this is not a character from the first series moving to the second series, but rather a periodic reminder, usually through guest appearance and crossover, of the connection between the two shows.

"Mork: Mork calling Orson....come in Orson.... Orson: Mork! This is not your usual day for reporting back to me! Mork: Ah, quite true your Immenseness! But see, I did a spin-on to pay back for my spin-off."
 * As the page quote indicates, The Simpsons mocks this idea in the Chief Wiggum, P.I. segment of "The Simpsons Spin-Off Showcase."
 * There's also The Lovematic Grampa from the same episode, where Homer stops by Moe's Tavern, and Abe calls his son out on the manner in which he buried his corporeal body ("You buried me naked and sold my suit to buy a ping-pong table!"). Homer responds by unplugging the love tester in which his father's soul resides and telling Moe, "Call me when you get a karaoke machine."
 * Law and Order Special Victims Unit had Briscoe and Green from Law and Order investigating a case that tied into Benson and Stabler's in "...Or Just Look Like One," and Abbie Carmichael served as the ADA in charge of SVU cases until they got their own ADA (first a minor character played by Reiko Aylesworth, then Alex Cabot). Furthermore, there was a crossover episode with the mothership, "Entitled," where SVU investigated the case in one episode and the DA's office prosecuted it in the next.
 * Law and Order: Criminal Intent followed the same pattern, with Briscoe and Green called upon to leak info of a serial poisoner by Goren and Eames in one episode, Van Buren asked about a suspect that formerly served under her in another episode, and Skoda called in for a psychiatric opinion in yet another episode. And before L&O: CI launched, there were plans for a "mega crossover" between the three series centered around a terrorist attack...but then 9/11 happened.
 * The short lived Law and Order: Trial by Jury also did this, once with a follow-up on a case that had been closed on SVU, and once with the prosecution of the guy who shot Det. Green on the original series.
 * Angel had Oz and Spike showing up in one episode to follow up on plot from Buffy, Buffy showing up in "I Will Remember You," and Faith fleeing to LA after the events of "This Year's Girl"/"Who Are You?" with Buffy pursuing.
 * Willow also showed up once to deliver news about Buffy, and again later when the AI team needed her to perform a spell.
 * Willow was the crossover once again in the season 9 comic series, appearing on the last page of Angel&Faith #10.
 * There was also a special crossover "event" between the Buffy episode "Fool For Love" and the Angel episode "Darla", in which several flashback scenes are seen from Spike's perspective in the Buffy episode and then again from Darla's perspective in the Angel episode which originally aired immediately afterward.
 * Season 6 and season 3 were the exceptions. Buffy changed networks in its sixth season and Angel's third and crossovers were banned. The reunion of Buffy and Angel after Buffy's resurrection was only visualized in comic book form. Fortunately, the networks changed the rules the next season And the Fandom Rejoiced.
 * Consciously averted with Joey, the spin-off of Friends, if only because it didn't last long enough for them to try. The character moved from New York to L.A. so that the writers wouldn't have to explain why his best friends never visited him—not that that worked for Frasier...
 * Doctor Who occasionally does this in reverse, with Capt. Jack returning and revealing his connection to Torchwood in the last three episodes of Series 3, and Torchwood and Sarah Jane getting caught up in the Series 4 finale. The producers have gone on record that the Doctor will never appear in Torchwood, as that would encourage Who's younger fans to watch a show which...isn't exactly aimed at them.
 * The Brigadier appears in the second season finale of the Doctor Who spinoff The Sarah Jane Adventures.
 * The Tenth Doctor appears in series three (The Wedding of Sarah Jane Smith"). The Eleventh shows up in series four (Death of the Doctor''), alongside another Classic Who companion, Jo Grant.
 * It also features a Sontaran, the Slitheen and a Graske as recurring enemies, with the Sontaran's story being a direct continuation of what the Doctor did on his show.
 * In Torchwood, Doctor Who companion and Jack Harkness' ally Martha Jones appears in a few series 2 episodes.
 * The episode "Cyberwoman" features a partially converted Cyberman from the aftermath of the Doctor Who series 2 finale.
 * The pilot of Mork and Mindy had a "flashback" (filmed for the show) where Mork pays a visit to the Fonz in the 1950s again. They even bring in Laverne from Laverne and Shirley.
 * Lampshaded by Mork himself as he reports to Orson after appearing as the new material holding together a "Happy Days" clip show later on in the season.

"Stanley Roper: Larry! I'm glad to see you! Larry: You never were this glad to see me when I was your tenent. Stanley Roper: I was when you paid your rent on time!"
 * Of course, Happy Days and Laverne and Shirley had several crossovers themselves when both shows were set in Milwaukee.
 * The second season premire of The Ropers featured a visit by Jack, Janet and Crissy. A later episode would have Larry Dallas dropping by.


 * The first season of Yu-Gi-Oh! GX easily bears the closest resemblance to the original Yu-Gi-Oh! and even contains Shout Outs like Sho fantasizing that he and Judai are Reincarnations of an Egyptian pharoah and high priest. From Season 2 onward, it steadily grew to more closely resemble, if anything, Neon Genesis Evangelion.
 * Pegasus and Kaiba appear with a fair amount of frequency on GX as well, and Sugoroku (Grandpa Muto) is featured briefly when the gang visit Domino City.
 * The first episode of each new Star Trek series featured a cameo appearance by one or more stars of a previous series.
 * DeForest Kelley (Dr. McCoy from Star Trek: The Original Series) showed up in the series premiere of The Next Generation as an extremely aged Admiral McCoy.
 * Star Trek: The Next Generation and Deep Space Nine crossed-over for the "Birthright" two-parter.
 * Deep Space Nine also brought Chief O'Brien over as a regular cast member from the beginning, in addition to having Lwaxanna Troi in a number of guest appearances. Even Kor, Kang, and Koloth from the original series showed up as guest stars.
 * Quark from Deep Space Nine appeared in season seven of The Next Generation; he was actually intended to be in an earlier crossover, until it was realized that episode would be airing before Deep Space Nine's premiere and Quark was rewritten as a generic Ferengi.
 * Voyager's mission in the pilot episode started from Deep Space Nine, and an early scene had Tom Paris rescue Harry Kim from one of Quark's scams.
 * In fact, both Deep Space Nine and Star Trek: The Next Generation featured season arcs revolving around the Maquis, which was created intentionally to serve as a plot device for Voyager's mission that resulted in it being stranded in the Delta Quadrant as well as its unusual crew dynamics.
 * Deanna Troi and Reg Barclay from The Next Generation both had recurring roles on Star Trek: Voyager.
 * Jonathan Frakes appeared in all three spin-off series (as William Riker in Voyager and Enterprise and as Thomas Riker in Deep Space Nine).
 * Voyager's Captain Janeway got to make an appearance in Star Trek: Nemesis, which was a Next Generation movie. A torch passed back.
 * Frasier eventually had all his old friends (except Rebecca Howe) from Cheers visit him at least once. Also, his ex-wife Lilith became a Recurring Character.
 * The creators have said that they chose Seattle specifically because it was on the other end of the country from Boston. A few thousand miles was enough to stop the higher-ups from pestering them all the time about when the Cheers gang was going to show up. It's not like Cafe Nervosa is on Cliff's mail route or anything...
 * The earlier (and much more obscure) Cheers spinoff The Tortellis had an episode where Cliff and Norm just happen to show up...in Las Vegas, where the show was set.
 * The Zeta Project had an episode featuring the second Batman; likewise, near the end of Batman Beyond, Zeta crossed back over.
 * Inverted with Osu! Tatakae! Ouendan 2!. For a limited time in 2007, Japanese gamers could go to download stations and download the Elite Beat Agents as playable characters.
 * The Man from U.N.C.L.E. and The Girl From UNCLE featured Leo G. Carroll playing U.N.C.L.E. chief Alexander Waverly in both series. In addition, Robert Vaughn appeared as Napoleon Solo in the The Girl From UNCLE episode "The Mother Muffin Affair", while Noel Harrison appeared as Mark Slate in the third season The Man from U.N.C.L.E. episode "The Galatea Affair".
 * The shows in Susan Harris' Miami sitcom universe (The Golden Girls, Empty Nest, Nurses) all featured these. There were two specific ones, specifically where events that began in The Golden Girls were brought to a close in the other two. A hurricane and a full moon began some chaos that would be fixed in the hospital where Harry Westen of Empty Nest and the Nurses worked. Might make it a Crisis Crossover.
 * Diff'rent Strokes and The Facts of Life had a number of these early in the latter show's run.
 * Meanwhile, a "connection" between Diff'rent Strokes and Hello Larry was contrived after the fact (having Mr. Drummond buy Larry's radio station) for the express purpose of setting up crossovers to try and help the latter show's popularity. It didn't work.
 * A Certain Scientific Railgun's spin-off protagonist Mikoto Misaka will (most of the time) run into the series protagonist Touma Kamijou. And most of the time, Mikoto will challenge Touma because of his Right hand cancelling her Railgun. And they'll tie.
 * The anime also threw in cameos of other Index characters, such as Aisa or Komoe. And the Fandom Rejoiced.
 * Just about the entire Mary Tyler Moore Show cast turns up in Rhoda for the title character's wedding, eight episodes or so into the first season. This is sweet, but a bit awkward...maybe WJM's ratings were so low, no one would notice if the news took a day off.
 * Hard to believe, but those who work in the news are allowed to have a day off. There is indeed a "weekend" crew at almost every local news outlet.
 * Similar to the Law and Order examples above, CSI occasionally does crossovers with its spinoffs. Aside from the pilot of one spinoff being an episode of a previous series, CSI: Miami and CSI New York crossed over once, and all three crossed over recently for a story involving human trafficking.
 * He-Man and the Masters of the Universe would often show up on She Ra Princess of Power.
 * Stargate Atlantis has featured each member of the original cast of parent series SG-1 in at least one episode each, often to contrast their spinoff counterpart. The producers make a deliberate effort to tie Atlantis back into SG-1, too - the original series got an episode set in the spinoff's location.
 * Stargate Universe has SG-1 characters turn up often (minus Teal'c who is Demoted to Extra, for some reason). O'Neill in particular is around more now than he was in the final seasons of his own series. The first season finale, involving SG-1 bad guys trying to reach the Destiny, is set to be as much an episode of SG-1 as SGU, if the episode that serves as prelude is any indication.
 * O'Neill's case makes a lot of sense, as he is currently the head of Homeworld Security, and the situation involving Project Icarus and Destiny are likely to need his oversight. You know, since Icarus Base was destroyed and most of the people in charge were killed or stranded on Destiny.
 * NCIS: Los Angeles, which got its start on a Poorly-Disguised Pilot on the regular NCIS, featured the DC team's Abby coming out to L.A. to investigate a serial murder case. The episode pretty much revolved around her.
 * Similarly, Bud Roberts from JAG appears on an early episode of NCIS.
 * Lee Wuan Kai, a Korean assassin, had a history with Leon Vance, director of NCIS. So, naturally, her first stop was Los Angeles not long after they get established, causing Leon to fly out to deal with things personally. Then she followed him back home.
 * In the very first Wario Land, a statue of Princess Peach is the game's MacGuffin. Mario himself appears at the end of the game to take the statue away from Wario.
 * In The Cleveland Show, one one-off gag features Chris appearing in Cleveland's house for no reason ("Go back to Quahog!"). Another episode features the death of Cleveland's ex-wife as an important plot point, giving an excuse for Quagmire and Peter to show up. Cleveland and his family also appeared in a Family Guy episode.
 * Intentionally avoided in Daria. Early on, it was decided that the program would be too different a show from Beavis and Butthead, and featuring characters from the previous series or explaining why the family moved from Texas to New England (aside from a throwaway line in the first episode about "uranium in the drinking water") would be confusing, misleading, and more likely to drive people off than attract them. Later on, they didn't do it simply because the show had become too established, and it would interrupt the flow and serve little purpose.
 * Edith Bunker dropped by to visit Louise Jefferson's deee-luxe apartment in the sky.
 * She and Archie also dropped in on her cousin Maude.
 * Hercules and Xena frequently crossed over into each other's shows.
 * As did several characters of varying importance (from gods to comic relief)
 * The Laird of the Glen's single appearance in I'm Sorry I Haven't a Clue might qualify. The Laird was created for the sitcom version of Graeme and Barry's "Hamish and Dougal" skits and played by Jeremy Hardy. So when Jeremy stood in for Graeme as Barry's teammate, it only made sense to do a "Dougal and the Laird" skit.
 * The Hamish And Dougal Hogmanay Special was a straighter example. Hamish And Dougal was spun off from I'm Sorry I Haven't a Clue, and the Hogmanay Special brings in all of Clue's regulars.
 * Done frequently with Dora the Explorer and its spin off Go, Diego, Go!.
 * Barney Miller's Dietrich stopped by to visit Fish in the latter's spinoff show.
 * Aoi Shiro has the appearance of Asama Sakuya from Akai Ito, who turns out to be Aoi-sensei's drinking buddy. The manga turn it Up to Eleven by.
 * This used to happen all the time in the Kamen Rider series starting with Kamen Rider V 3. With V3, Ichigo and Nigo helped turned Shiro into the titular Rider before they were supposedly killed. Then they came back to help him and Riderman. Then, every series afterward up to Kamen Rider Black RX would have every previous Rider return to help the current Rider save the day.
 * Several major characters from The Wotch make significant or cameo appearances in Cheer. For example, the arc where Alex tries to find new cheerleaders has Wolfie and Ming try out and make the cut, while Jason is bribed into helping with the tryouts.
 * Happened several times in the CSI franchise.
 * In season 9, Ray Langston appeared on both of the other series during a three-episode arc. It began on CSI, went to CSI: Miami and then to CSI: NY, before ending back on the original CSI.
 * CSI and CSI Miami had a two episode crossover. Mac went down to Florida in "Felony Flight" and Horatio followed Mac back to New York in "Manhattan Manhunt".
 * Just after the premiere of the Bones spinoff The Finder, Lance Sweets appeared on a an episode. Jack Hodgins also subsequently appeared in another The Finder episode.
 * Power Rangers Lost Galaxy, first spin-off in the Power Rangers franchiche, had main cast and characters from previous series, Power Rangers in Space (last series in "Zordon Era") teaming up to fight revived Psycho Rangers. Not only that but . Since then it became tradition for new Power Rangers series to have a crossover with previous one. Notable among them are Power Rangers Wild Force, which featured usual crossover with previous series as well as Forever Red - episode featuring every single Red Ranger in the history of the franchiche teaming up - and Power Rangers Dino Thunder, which not only did a crossover, but also had Jason David Frank return as Tommy Olivier, Green Ranger of the original series, who was regular character and took a mantle of Black Ranger.
 * There were two crossovers between Dino Thunder and SPD, with each team getting to visit the setting of the other's show.
 * The connection between Power Rangers Lost Galaxy and the "Zordon Era" was established in the very first episode of "Lost Galaxy". Bulk, Skull and Professor Phenomenus appeared.
 * Notably averted in Boston Legal, where none of the regulars on The Practice stopped by for guest spots (likely attributed to the spinoff characters having been introduced as stars of the latter's final season). This can alarm some viewers who notice that guest stars on The Practice like John Larroquette and Rene Auberjonois ended up starring on Boston Legal as completely different characters.
 * Bill Smitrovich, who portrayed Assistant District Attorney Kenneth Walsh in The Practice, portrayed another prosecutor in Boston Legal. Smitrovich's character in the spinoff worked in a state where death penalty was an option.
 * The law firm of Young, Frutt and Berlutti was once mentioned in Boston Legal.
 * In The Perils of Penelope Pitstop, there was a scene where the Hooded Claw asked Penelope if she was expecting Dick Dastardly.
 * The main field cops of Tokkei Winspector returned for a three-part episode of Tokkyuu Shirei Solbrain. It was only some episodes later one of them became a regular in Solbrain.