Henry Darrow and David Janssen were both in Harry O and the mini-series Centennial. (I have watched way too much TV my entire life :()
Do spinoffs count? Harry Morgan, Jamie Farr, and William Christopher were all in AfterMASH, the spinoff of MASH*. The former show lasted 25 episodes, which is way more than I would have guessed.
Scott Baio had a recurring role in AD as well, so that makes our first trio. (Though the OP is asking for “costars” rather than supporting characters/narrators…)
How is Bea Arthur not what you were going for? The show’s name was Maude(?) She’s no different than MTM or Bob Newhart. In GG, all three of the women (Bea, Rue and Bett) were considered stars. They weren’t “regulars”–they were the show. 
And that reminds me: Vicki Lawrence–a costar on Carol Burnett, a star of Mama’s Family.
We’re looking for pairs of people who both starred together on more than one show.
Lee Majors, Big Valley, Six Million Dollar Man, The Fall Guy.
Umm…they were all playing their original characters from MAS*H though. Read the title of the thread.
Lee Majors is one person. The OP is looking for PAIRS of people going to on the star TOGETHER in two or more shows.
Tina Fey, Tracey Morgan on SNL and 30 Rock.
Brad Whitford, Matthew Perry on The West Wing and Studio 60 on the Sunset Strip.
Sarah Michelle Gellar, Michelle Trachtenberg on All My Children and Buffy the Vampire Slayer.
Johnathon Frakes and Mariana Sirtis were both in ST:Next Generation and Gargoyles togeather, though wikipedia is ambiguous on whether they were listed as regular cast or not on the latter show.
Star Trek cast members seem to follow each other around a lot (Gargoyles had almost the entire cast as recurring characters at one point or another, Boston Legal has two ex-Trek regular cast members and has also had several guest stars, Stargate Atlantis has had several, etc. I can’t think of any other case where two from the same Trek spin-off were regular cast members on another show, though.)
Weren’t Jewel Staite and Morena Baccharin (from Firefly) together on Stargate Atlantis? Or did they split up between SG:SG1 and SG:Atlantis?
Michael Boreanaz, Alexis Denisoff, James Marsters and Charisma Carptnter on Buffy and Angel.
Colm Meany, Michael Dorn and Rosalind Chao on TNG and Deep Space Nine.
Hugh Laurie, Stephen Fry, A Bit of Fry and Laurie and Wooster and Jeeves.
Dan Castellaneta and Julie Kavner, The Tracey Ullman Show and The Simpsons.
Except for Fry and Laurie, these are all the same characters so they don’t meet the requirements in the OP.
And Fry and Laurie were both in several seasons of Blackadder, so they’ve got another show.
Not that I know of, but Ben Browder and Claudia Black from Farscape both worked on Stargate SG-1.
There was a well-known example from the soaps. During the mid-70s, the NBC soap “Another World” featured an enormously popular couple Steve & Alice (perhaps the most popular soap couple up ever until Luke & Laura showed up a few years later), but the head writer took a dislike to the diva-ish actors playing them and had them both written out - the couple broke up, Steve was killed off, and Alice recast with another actress and significantly downplayed in the storyline. Meanwhile, the ABC soap “One Life to Live” (which happened to be airing directly opposite “Another World”) was close to being cancelled at the time. The producers of “Life” immediately hired both actors to play new characters on that show who had been lovers who had broken up, but were now reunited. So, “Life” efffectively just carried on the storyline that their competitors had discontinued. Apparently, the gimmick worked, and a lot of “Another World” fans started watching “One Life to Live” instead.
Just to complete the ways the question could be misunderstood:
How about my uncle Keith? He he has never appeared in a TV show.
Morena was only on SG:1 and Jewel Staite was only on SG:Atlantis.
I guess if we count Whoopi Goldberg as a co-star of TNG (wikipedia has her listed as a “secondary main character”), then her and Levar Burton were both voice actors on Captain Planet.
:smack:
Directors sometimes take their stable of actors with them. Someone already mentioned Aaron Sorkin, (West Wing and Studio 60,) and also Chuck Lorre. (Roseanna and Big Bang Theory.) Joss Whedon has had several shows and likes to reuse talent, but the only pair I can think of offhand is Eliza Dushku from Buffy (only guested on Angel) and Amy Ackerman from Angel both being on Dollhouse. So that doesn’t count. Plus, to my knowledge Joss has never had a successful show. (Not that Studio 60 was either.)
I’m guessing David E. Kelley (Ally McBeal, The Practice, et al) reuses talent, but I’m not really a fan of his and have never watched any of his shows.
Krokodil said:
[cough]David[/cough] Sorry, something got caught in my throat.