Two examples:
Charlie Sheen and Jon Cypher, the Harper brothers in Two and a Half Men, were both in the 1991 movie Hot Shots.
Alice Ghostley and Marion Lorne, the bungling Esmerelda and Aunt Clara in Bewitched, respectively, appeared together in the hotel lobby scenes in 1967’s The Graduate. (Ghostley would essentially replace Lorne in the TV series when she passed away shortly thereafter.)
Any others?
Car 54 had Fred Gwynne and Al Lewis before starring together on the Munsters.
Tom Poston was on at least one episode of The Bob Newhart before being with him as a regular on Newhart.
Tony Danza and Danny DeVito of Taxi made a crappy movie together. Going Ape!
Speaking of which, Christopher Lloyd and Danny were in One Flew Over the Cuckoo’s nest before Taxi.
This happened all the time.
An excellent example (Gwynne and Lewis), should have thought of it first!
Kristin Johnston & French Stewart appeared together for 6 years on 3rd Rock from the Sun in the late 1990s, then again for two years on Mom in the early 2020s.
Johnny Galecki starred in The Big Bang Theory, and two actors with which he’d appeared in Roseanne had recurring roles on BBT. While Sara Gilbert & Laurie Metcalf were on Roseanne from day 1, to the end, and appeared in nearly every episode, Galecki was a Roseanne regular for just a couple of seasons.
Then there are the groups of actors that made movies together.
Astair and Rogers.
John Wayne and Maureen O’Hara
The Mel Brooks regulars, etc.
Rat Pack
Brat Pack
Frat Pack
Will Arnett and David Cross appeared together on Arrested Development before The Increasingly Poor Decisions of Todd Margaret.
Hank Azaria and Yeardley Smith appeared together on The Simpsons before Herman’s Head.
They were both on King of the Hill as well, IIRC.
Weird one, The Elka Summer’s movie, The Wicked Dreams of Paula Schultz had Bob Crane, John Banner, Werner Klemperer and Leon Askin of Hogan’s Heroes.
Bob Denver and Tina Louise both appeared in For Those Who Think Young (1964) which premiered a few months before Gilligan’s Island. I do not recall that they had any scenes together in the film.
Vic Morrow (Sgt Saunders on Combat!) and Jack Lord (Steve McGarrett on Hawaii Five-O) faced off in episodes of both series.
Alan Tudyk and Nathan Fillion did all 14 episodes of Firefly together. Then Fillion was in 16 of the 25 episodes of the largely forgotten Con Man which starred Tudyk. In turn Tudyk has been in 2 episodes of Fillion’s The Rookie.
And Fillion voiced the Octopus on Resident Alien.
I see a pattern now:
Can’t believe I forgot this-- 2 years before Xena, Warrior Princess premiered, Renee O’Connor, the actress who played Gabrielle, was in a TV movie called The Flood: Who Will Save Our Children? along with David Franklin, the actor who would play Brutus in the 4th season of Xena. He’d only be in a handful of episodes, but they were all pivotal and intense.
[slight hijack] I have always loved Cesar’s delivery of the line “And you, Brutus?” on Xena. He says it like a dare. [/slight hijack]
Downton Abbey starred Brendan Coyle and Hugh Bonneville as Mr. Bates and Lord Grantham, respectively. These parts made these guys’ careers, launching them to superstar status.
However, a dacade and half earlier both men appeared in the Bond film Tomorrow Never Dies in blink-and-you’ll-miss-them bit parts. Bonneville had a speaking part, I don’t believe Coyle did. I believe they were in the same scene together. They both played sailors on the British ship that was firing on the stealth boat near the end of the movie. Both actors had almost no screen time previous to this.
Two more from Arrested Development: Alia Shawkat had a recurring role on season 4 of Transparent, which starred Jeffrey Tambor.
Drew Carey and Ryan Stiles appeared together on The Drew Carey Show before (and while) reuniting for the American version of Whose Line Is It Anyway?
Jerry Van Dyke (Dick’s brother) appeared alongside Mary Tyler Moore in episodes of both DVD and MTM.
Andy Griffith and Don Knotts were in No Time For Sergeants before The Andy Griffith Show.
Jack Hogan (Pvt Kirby on Combat!) was on Hawaii Five-O as well.
Before Star Trek, William Shatner and Leonard Nimoy worked together in an episode of The Man from UNCLE (“The Project Strigas Affair”),