John Ritter can’t be the “breakout” star of the series because he was the main character from the beginning. He was credited first, he had the majority of his scenes, and he was the main character. All three of those things are incompatible with someone being the breakout character, the person asking the question.
Joyce DeWitt: Honestly, I have to assume this question is trolling because it seems to imply that you haven’t seen the show or have only seen a few episodes.
DeWitt:
Rarely has an episode that is solely about her or she is the reason for the “A” story of the episode.
Not a particularly skilled comedic actor
Disappeared into the background when Suzanne Sommers (the REAL breakout star of the series) emerged.
Still stuck around midway through Sommers was fired and two other actors were hired to replace her.
Often overshadowed by characters like The Ropers, Mr. Furley, Larry, the used car salesman upstairs, etc. Even Lana, who was hired to create a sexual relationship with Ritter’s Jack Tripper in season four, often got more attention than DeWitt.
Joyce DeWitt was essentially the “third” or “fifth” wheel of the show, whichever worked best when she was on screen. She couldn’t build a successful character because she was overshadowed by Ritter’s humor, Sommers’s popularity, and the great timing of Ropers and Furley (comic legend Don Knotts). This only got worse when Sommers was dropped and two other “blondes” were added to the cast.
NOT a breakout character.