Not a co-star but the main character. The one that comes to my mind is Roseanne Barr being fired from “Roseanne”.
The show needn’t be named for the actor like my example was.
Valerie Harper left in a salary dispute I believe from the show that went from being called Valerie to Valerie’s Family to The Hogan Family. She was on it for only the first 2 years of its 6 year run.
Threes Company re: Suzanne Somers.
The only trick is she was the #2 on the show and not the #1 star. Not quite the same thing.
John Ritter was the star of the show. Same for the male character in the English Sitcom it was based on Man About the House. The male character of Robin was the prime star.
I think the OP had the example of the biggest. I don’t know if we’ll find any bigger stars kicked off their own shows!
That being said, I have an example of another creator being kicked off their own show. Very tiny creator with a very tiny show. A cartoon on the CN called Clarence was created by and ran by Skyler Page (who also did the voice of the main character), who was accused of sexual assault after the first season and let go by Cartoon Network. The show went on for 3 more seasons without him.
What about Charlie Sheen and “2 1/2 Men”?
Charlie Sheen seems like a great example. Without question the #1 on the show.
Minor one, Ruby Rose, the terrible actress was fired/left Batwoman after the first season. This terrible show only went one more year without her.
When Toper Grace (Eric Forman) left The 70s show, it was 100% his decision, so that doesn’t count. Also while he was the central character, I’m not sure he was still the #1 character when he left.
ETA: Clooney leaving ER and Steve Carrell leaving The Office were big, but also the actors’ decision. The shows wanted them to stay.
David Duchovny quit the X-files after season 6 or so. It went on for three more seasons where he only appeared sporadically.
Polly Holliday, one of the stars of the sitcom Alice (but not the title character) quit about halfway through the show’s run.
If we are sticking with “kicked off” instead of just leaving, which most of this examples are, I have to go with Justin Roiland from Rick and Morty. He wasn’t just the main character, he was the two main characters and several supporting ones.
And we should add Justin Roiland to that list.
ETA: DigitalC is a ninja.
Steven Hill was the lead character for the first season of Mission: Impossible. He was in a more orthodox sect of Judaism and wouldn’t work on the Sabbath. Other disputes developed, and his role was reduced and replaced by Peter Graves for the second season. Hill wound up leaving acting for close to a decade, then returned and ultimately wound up on Dick Wolf’s original Law & Order for many years.
He was being problematic. He made it clear he wanted bigger roles as an actor, felt playing a teenager was beneath him. His part was being reduced in importance as a result, but as you say, he made the decision to leave. Didn’t turn out the way he thought it would. Karma is a bitch.
Topher Grace’s movie career has gone pretty well, while the season of That 70s Show without him… didn’t.
Cite?
That career in movies seems pretty minor to me. Not that he made the wrong decision, but I think far from pretty well.
Plenty of work but hardly a star is what I see:
FTR: I think the answer is somewhere in the middle, not karma is a bitch and not gone pretty well.
Kevin Spacey was kicked off House of Cards due to sexual allegations against him, and the show proceeded to its final season without him.
If we’re going to talk about Topher Grace leaving That 70’s Show, we should also mention Ron Howard leaving Happy Days. Another case of the lead character’s actor deciding to move on. Although Howard’s post sitcom career has been a lot more successful.