I Want You to Meet An Old Friend of Mine

""Don't I know you?""

- Lord Vultare to Baydool, Quest of the Delta Knights

A guest appearance by someone with a personal or prior professional relationship with one of the cast members of the show, such as Rhea Perlman appearing on Becker, Christopher Lloyd appearing on Spin City, or Helen Hunt appearing on The Simpsons. More often than not the guest actor will be playing an Old Friend of the relevant character, whom they haven't seen in years.

Subtrope of Casting Gag. Liable to be a Large Ham. Expect numerous Actor Allusions. Compare Real Life Relative. Not to be confused with Old Friend or Beleaguered Childhood Friend, but can overlap with either.

Anime

 * Episodes 42 and 43 of the Angel Heart anime series involves Ryo Saeba (who is voiced by Akira Kamiya) dating a news reporter voiced by Yuriko Yamamoto. Kamiya and Yamamoto previously played Kenshiro and Yuria in the original 80's version of Hokuto no Ken.

Film
"Crow: "David Warner, you're under arrest by the order of David Warner!""
 * Extreme example: All sorts of hilariously awkward dialogue of this sort occurs between the Big Bad (David Warner) and The Mentor (David Warner) in the MST3K-featured film Quest of the Delta Knights.


 * In Maverick (directed by Richard Donner), Bret Maverick (played by Mel Gibson) is in a bank that is held up by a gang, one of whom is played by Danny Glover (Gibson's co-star from the Lethal Weapon movies, also directed by Donner); the two men almost appear to recognise each other, but then dismiss the notion. (Then, to cement the association, as Glover's character is mounting his horse for a getaway he is heard to say, "I'm gettin' too old for this shit!" - Glover's famous catchphrase from Lethal Weapon.)
 * In the epilogue of Harry Potter and the Deathly Hallows, Part 2,.
 * In The Senator Was Indiscreet, a William Powell vehicle, the final scene reveals that his wife, unseen till now, is Myrna Loy, who co-starred as his wife in numerous movies including The Thin Man series.

Live Action TV

 * In Doctor Who the actress who plays Jenny, the Tenth Doctor's daughter, is the daughter of Peter Davison, the Fifth Doctor.

"No, it's not just Scrubs in Florida with a lot of wine."
 * Bob Newhart's first sitcom wife, Suzanne Pleshette (in The Bob Newhart Show), showed up in the final episode of his second sitcom (Newhart), where it turned out the whole later series (in which he played a New England innkeeper).
 * Tom Poston, who played George Utley on Newhart, had been a recurring guest star on the earlier show as "The Peeper".
 * One episode of the later show had Newhart's Dick Loudon running into the first show's Mr. Carlin (Jack Riley).
 * Bill Daily (annoying neighbor Howard Borden from The Bob Newhart Show) guest-starred as Dick Loudon's annoying neighbor on Newhart.
 * Timothy Daly appeared as himself in an Episode of Monk. He and Monk star Tony Shalhoub previously appeared together in the series Wings.
 * Lampshaded by the fact that Monk doesn't know who Tim Daly is. His assistant tells him that Daly was on Wings and was the only good actor on the show.
 * In another episode, Steven Weber, also from Wings appeared. He was not playing himself, however, and no mention of the show was made.
 * The secretary  in Sherlock is the girlfriend of Benedict Cumberbatch, who plays Sherlock.
 * Nash Bridges had a double-header with the episode "Wild Card", reuniting stars Don Johnson and Cheech Marin with their former partners Philip Michael Thomas and Tommy Chong. Thomas's character even made a second appearance in season six's "Out of Miami".
 * When Brad Pitt appeared on Friends, his character was an old acquaintance of Jennifer Aniston's . However, he hated her and she barely remembered him.
 * As well as Tate Donovan, who appeared earlier on the same show when he was dating Jennifer Aniston.
 * As well as Julia Roberts, who dated Matthew Perry, and David Arquette, who married Courteney Cox.
 * Bruce Willis also appeared for a guest run, free of charge, after losing a bet to Matthew Perry on the set of their film The Whole Nine Yards. Similarly, Willis's character intimidates Chandler a bit (although moreso Ross, who's dating the daughter of Willis's role) just like in the movie.
 * With Lampshade Hanging, Michael J. Fox's last episode of Spin City began with him complaining over the phone to his therapist for sending him to meet with a substitute. He says, "You're almost like a father to me. How am I supposed to have that with some new guy?" and in walks the substitute therapist, played by Michael Gross, who played Michael J. Fox's father in Family Ties.
 * Another episode had Christopher Lloyd appear as Fox's old mentor, complete with Back to The Future lampshading.
 * And one episode had Meredith Baxter (Fox's mother on Family Ties) as his character's mother.
 * Likewise, the late David Carradine guest starred on Lizzie Mcguire as an old friend of the father who was "Like a brother to me." The actors actually were brothers.
 * Between the three of them, Stargate SG-1, Andromeda and Farscape pulled this numerous times: Michael Shanks and Christopher Judge both detoured from the SGC to appear as AI Avatars in an episode of Andromeda. Claudia Black's second guest appearance on Stargate SG-1 coincided with Ben Browder's introduction to the cast(with, as SG-1 is wont to do, Lampshade Hanging), and with the guest appearance of Lexa Doig (who played the titular Andromeda's several humanoid forms--and is actually married to Michael Shanks).
 * Also, Richard Dean Anderson knew Chris Judge and Don S. Davis from MacGyver.
 * Michael Shanks was the guest star of one episode of Sanctuary, a show on which Amanda Tapping has the lead role.
 * Cast as Peter Hunt, an old flame of Candice Bergen's titular character Murphy Brown, Scott Bakula ended his recurring role on the show by entering an elevator and "leaping" a la Quantum Leap, which series had recently ended.
 * Bakula then showed up as an old flame of Shirley Schmidt on Boston Legal. Shirley is, of course, played by Candice Bergen.
 * Scott Bakula also was imprisoned by his Quantum Leap sidekick Dean Stockwell in Star Trek Enterprise.
 * Bill Cosby welcomed Robert Culp onto The Cosby Show episode "Bald and Beautiful", reprising their teamup in the Spy Drama I Spy.
 * Gilmore Girls: In one episode near the end of season 4, Michael DeLuise's character's bachelor party includes his real-life brother, David DeLuise. To top it all off, the Girls are seen watching a movie starring Michael's father, Dom DeLuise. All of the above DeLuises have also had small parts on Stargate SG-1 and Sea Quest DSV.
 * Michael, Peter and Dom DeLuise also appear as siblings and father respectively for David's character in an episode of 3rd Rock from the Sun.
 * Gratuitous example: Tea Leoni (Mrs Duchovny) and Garry Shandling appearing in The X Files as themselves playing Mulder and Scully in a movie.
 * in Eight Simple Rules, Cate Hennessey (played by Katey Sagal) encountered an old boyfriend named Matt...who is played by Ed O'Neill, aka Al Bundy.
 * Tom Wopat appeared as an old friend of John Schneider's Jonathan Kent character on Smallville. Both actors starred on The Dukes of Hazzard.
 * A double helping happened on the same show, when Margot Kidder showed up, playing a colleague of Christopher Reeve's character. They were never in the same episode, but still...
 * They even had some MythologyGags for each. With the Wopat/Schneider reunion, they had them riding around in Wopat's character's car, which looked suspiciously like the General Lee, and even repeated the old Dukes of Hazzard gag of the passenger side door not working and having to climb in through the window. Lex referred to Wopat as Jonathan's "Good Ole Boy", a reference to the Dukes theme song. They even mentioned several NoodleIncidents involving Jonathan and Wopat's character outrunning the local sheriff when they were young!
 * As for the Margot Kidder character, Martha questions whether Kidder's character and Chris Reeve's character ever had a relationship, to which Kidder's character wistfully replies "In another lifetime..."
 * Tahj Mowry, younger brother of Tia and Tamera Mowry, guest starred three times on their show Sister Sister (this is also an example of a You Look Familiar, since he played a different character each time.) They returned the favor by appearing on his show, Smart Guy.
 * In an episode of Boy Meets World, one of Cory's college professors is played by Fred Savage, the brother of Cory's actor, Ben Savage.
 * Eric Matthews' best friend Jason was played by Will Friedle's real-life best friend Jason Marsden. This isn't the first of last time the two of them played a pair of Heterosexual Life Partners
 * In the Pamela Anderson sitcom Stacked, Pam's character gets visits from old friends played by Carmen Electra (Anderson's co-star in Baywatch) and Jenny McCarthy (who appeared with Anderson in Scary Movie 2). All three have also been Playboy Playmates.
 * Carmen Electra was never actually a Playmate, she just posed for the magazine. Several times.
 * In the S1 finale of the (surprisingly watchable) Courteney Cox Arquette vehicle Di RT, Jennifer Aniston turns up as a rival tabloid editor. They actually kiss, in front of some people at the newsdesk
 * Almost subverted in Babylon 5. When June Lockhart made a guest appearance, J. Michael Straczynski refused to write a scene in which her character meets Lennier, played by her Lost in Space co-star Bill Mumy, as there was no logical reason for the two to meet except for such a joke. However, Mumy himself wanted to do an in-joke about it, and so without permission he snuck into one of her scenes out of his alien makeup as an extra and gave a quick smile to her.
 * In an episode of Coach, Luther (played by Jerry van Dyke) learns that he was adopted and ends up attending a reunion of his birth family. As he enters he complains to Hayden that there's no way he could be related to any of these people. An unnamed character (played by Dick Van Dyke) chooses that moment to walk conspicuously across the set.
 * Adrian Edmondson could have been cast in Blackadder Goes Forth for the sole reason of appearing against Rik Mayall, his long-time work partner. In their double-act most of the constant violence (and occasional gay jokes) are directed at Mayall, so it seems too much of a co-incidence that and loudly proclaims "What a poof!"
 * What I Like About You brought in (in various episodes spread throughout 4 years): Chelsea Brummet (of Amanda Bynes' first show), Sparkle (from Bynes' film Big Fat Liar), Tamara Mello (of Leslie Grossman's previous show), and three of Jennie Garth's ex-co-stars (Ian Ziering once, Jason Priestly twice, & Luke Perry thrice).
 * Does it count if the two were never on the show at the same time? Because Amanda Bynes was on All That before the complete-cast makeover; Brummet was after the reboot.
 * See below; Bynes guest-starred in a post-reboot episode.
 * On a similar note, All That post-reboot often played around with this, bringing on former cast members as guest stars (and also having a hilarious interaction between guest star Britney Spears and recurring character Thelma Stump, played by Britney's younger sister Jamie Lynn.)
 * Amy Sedaris' interview on The Colbert Report for the Strangers With Candy movie should have been one of these, but the character Stephen Colbert wasn't in Strangers With Candy. It turns out in the Report universe, Chuck Noblet was played by Kevin Spacey.
 * Spin City's Richard Kind, Michael Boatman, Alan Ruck, Barry Bostwick, Alexander Chaplin, Heather Locklear and of course Michael J. Fox have all appeared in Bill Lawrence's next show, Scrubs.
 * Mandy Moore guest-starred as a love interest to then-boyfriend Zack Braff in season 5.
 * Angel co-stars Christian Kane (Lindsey McDonald) and Sam Anderson (his evil boss Holland Manners) were reunited in an episode of Leverage. Kane (Eliot Spencer) was part of a con against Anderson's one-episode character, and says that they winked at each other on-screen to reference their history.
 * Sam Anderson and Daniel Dae Kim co-star in Lost. They don't share a few quips about going from playing evil lawyers to castaways on a weird island?
 * Another example with Angel actors: David Boreanaz went from playing the title character in Angel to Agent Booth in Bones. While there, he encountered Adam Baldwin, who played both a fellow FBI Agent (Bones) and a liaison to the Senior Partners (Angel), and Gina Torres, a murder suspect (Bones) and a demoness (Angel). Interestingly, although Baldwin and Torres did not appear in the same episode, both were regulars on Firefly, which was also by Joss Whedon, the creator of Angel.
 * And Bones regular TJ Thyne (Dr. Jack Hodgins) had unnamed guest spots in the final seasons of Angel.
 * From another direction, Bones had a one-off episode in which Bones' second cousin appears. Who else should show up in such a role other than Emily Deschanel's little sister Zooey?
 * In Plain Sight stars Mary McCormack, who played Kate Harper on The West Wing. In the second season, her character's sister dates a character played by Joshua Malina. Malina's and McCormack's characters dated on TWW, and there is an odd look when their characters meet. Also, in the same episode, fellow The West Wing alum Richard Schiff guest stars (as The Implacable Rabbi Detective), and he and McCormack share a classic Sorkin Pedeconference through the halls of a hospital at the end of the episode.
 * In The West Wing, Martin Sheen offers William Devane the job of vice president. The last time they faced each other in the oval office was in the 1970's, in The Missiles of October, when they played Robert and John F. Kennedy respectively. Both were doing Mayor Quimby accents back then, of course.
 * The Buffy the Vampire Slayer fifth season opener was "Buffy vs Dracula", billed as a battle of the titans. It was a little undercut by Dracula being played by Sarah Michelle Gellar's old flame from "All My Children", Rudolf Martin.
 * On Arrested Development, David Cross's character goes to a therapist played by Bob Odenkirk, his Mr. Show co-star.
 * Glee: Jonathan Groff's appearance as Rachel's beau Jesse St. James. He and Lea Michele (Rachel) were co-stars in the Broadway run of Spring Awakening. An ex of hers, John Lloyd Young, actually appeared in the third episode ("Acafellas") but their characters never interacted.
 * Becker, starring Ted Danson, has featured guest appearances from his Cheers co-stars Rhea Perlman, George Wendt and Kelsey Grammer, all of which are subtly lampshaded by means of role-reversal; Perlman plays a happy-go-lucky character to Danson's unhappy pessimist, Wendt plays a barman to Danson's character, and Grammer plays a recovering alcoholic against Danson's Harvard-graduate doctor. In Grammer's case, the two old friends also state that the last time they saw each other was in a bar in Boston.
 * It happened a number of times in News Radio.
 * In "Stupid Holiday Charity Talent Show", Dave's knife-throwing nemesis Throwdini is played by Dave Foley's former and future Kids in The Hall colleague Kevin McDonald.
 * In "Goofy Ball", Bill's stalker is played by Phil Hartman's former Saturday Night Live colleague Dennis Miller.
 * Janeane Garofalo and Bob Odenkirk also made guest appearances; both worked with Andy Dick on The Ben Stiller Show.
 * Following the ending of The Fresh Prince of Bel Air, Alfonso Ribeiro, who had played Carlton Banks, joined the cast of In The House as Dr. Maxwell Stanton. In the finale of that show, Max's parents appear -- naturally, played by James Avery and Daphne Maxwell Reid, who had played Carlton's parents. Later a minister appears, played by Joseph Marcell, who had played Geoffrey Butler on The Fresh Prince Of Bel Air. Topping off the gag, Max's father mistakenly gives the minister a drink order, then comments that he "looks like someone we used to know".
 * In Bottom, Christopher Ryan -- who played the suave Mike alongside series writers-stars Adrian Edmondson and Rik Mayall in The Young Ones -- occasionally shows up as Dave Hedgehog, the decidedly less suave friend of Edmondson's character Eddie.
 * Lindsay Lohan, then-girlfriend to Wilmer Valderama appeared on That 70's Show as a customer Fez later went out with in season 7.
 * Chris Masterson guest-starred in a few episodes, and had at least one scene with Hyde, who is played by Chris' older brother Danny.
 * Robert Carradine once guest-starred on an episode of ER where he had a scene with Anthony Edwards detailing all the ways the hospital could be improved. Carradine and Edwards co-starred in Revenge of the Nerds.
 * I Carly had an episode where Miranda Cosgrove's real life best friend Haley Ramm play a childhood friend of hers that she hasn't seen in years in the episode iReunite With Missy
 * Haley also appeared in Yours Mine Ours as Miranda's character's step-sister.
 * Florence Henderson and Robert Reed guest-starred in separate subplots on an episode of The Love Boat. They meet at the buffet table, look as if they're about to recognize each other, then shake their heads dismissively and go their separate ways.
 * In the Kenan and Kel episode "Poem Sweet Poem," Philip (one of Kenan and Kel's school friends) is played by their old pal Josh Server.
 * Lisa Edelstein appeared in two episodes of The Good Wife early in season three, playing Celeste Serrano, a former colleague and former lover of Will Gardner, played by Josh Charles. Edelstein also appeared in two episodes of the show Sports Night, in which she played Roberta "Bobbie" Bernstein, a colleague and former lover of Dan Rydell, who was played by Josh Charles.
 * CSI: NY had two. One of Gary Sinise's costars from The Stand miniseries appeared in the season one episode "Night Mother", though they had no scenes together. More prominently was Mac's boss Sinclair played by the actor who played alongside Gary as Bubba in "Forrest Gump".
 * Dallas had Barbara Eden on for a few episodes as Lee Ann De La Vega. J.R. greeted her first appearance with "Haven't I seen you somewhere before?"
 * On NCIS, after Abby discovers, she tracks down her half-brother. The actor who plays the brother is Pauley Perrette's real life ex-boyfriend turned close friend; Pauley urged her Twitter followers for months to lobby for him to be cast.
 * Cougar Town got a lot of mileage from the regular and recurring cast of Scrubs, which was also created by Bill Lawrence and featured Christa Miller in a big role. This got confusing when Ted the Lawyer showed up in Cougar Town, and hilarious when Ted stopped by the cauldersac and freaked out because everyone looked like someone he used to work with.


 * The Middle has done with Doris Roberts in a recurring role in its second season and Ray Romano in the third-season premiere. Both were, of course, castmates of star Patricia Heaton previously on Everybody Loves Raymond.

Theater

 * Catherine Tate and David Tennant of Doctor Who fame were reunited for an onstage production of William Shakespeare's Much Ado About Nothing. They are both prominently featured in its advertising.
 * The Joss Whedon modern-dress film of Much Ado About Nothing is stacked to the gills with alumni from various Whedon shows and movies.

Western Animation

 * One of the best moments of Shark Tale was when Robert De Niro said to Martin Scorsese, "We've worked together for a real long time."
 * In the Batman the Animated Series episode, "Beware the Grey Ghost", the Gray Ghost (a thinly veiled black and white Batman TV show copy) is voiced by Adam West.
 * The Grey Ghost is also inspired by The Shadow, who himself inspired Batman.
 * In Batman the Brave And The Bold Blue Beetle's best friend Paco is played by Jason Marsden, who previously played Eric Matthews' best friend, er, Jason Marsden on Boy Meets World, and is Will Freidle's best friend in Real Life.
 * This sort of thing happens a lot with these two.
 * Also from Batman the Brave And The Bold, Kevin Conroy, the voice of Batman from the 90s animated series, played the Phantom Stranger in "Chill of the Night!" alongside Mark Hamill, who famously played the Joker in that series, as the Spectre. The episode also featured Adam West as Thomas Wayne and Julie Newmar as Martha Wayne.
 * The episode of The Batman that introduced Robin featured Kevin Conroy (Batman from B:TAS) as Dick Grayson's father and Mark Hamill (Joker from same) as Tony Zucco.
 * Also from the episode that introduced Robin with Mark Hamill was Grey Delisle, who voiced Dick Grayson's mother. Hamill and DeLisle voiced father and daughter Ozai and Azula on Avatar: The Last Airbender.
 * When Pleakley's family comes to visit on Lilo and Stitch The Series, they are voiced by many of Kevin MacDonald's former castmates from Kids in The Hall. The only Kid in the Hall who didn't voice a family member voiced a preacher in that episode.
 * In the sequels to Disney's Cinderella, Prince Charming is voiced by Christopher Barnes and Cinderella herself is now voiced by Jennifer Hale, AKA The Black Cat from the same series.
 * Also, during the run of said series, Robert Hays reprised his role of Iron Man for some team-ups with Spider-Man. Hays and Barnes previously appeared together on the Starman TV series and both were reportedly thrilled with working together again.
 * Tara Strong and Cree Summer have been friends since childhood, even growing up together, and these days do a lot of voice-over work together. In other words, if you hear one of them in a given series, you're likely to hear at least one of the other two in the same series at some point.
 * They've done enough shows together that their respective characters eventually parodied the infamous Sweeps Week Lesbian Kiss.
 * In The Simpsons, Sideshow Bob is played by Kelsey Grammer. His brother and father are played by David Hyde Pierce and John Mahoney respectively, who played Frasier's brother and father.
 * Brenda Song played a rival to Ashley Tisdale's Candace on Phineas and Ferb.
 * Thomas Sangster played a young boy with a Precocious Crush on Olivia Olsen's character in Love Actually--so when they were cast Ferb and Vanessa, Ferb's crush on Vanessa became a running gag.