Character mistake: When Jack tells Mr. Furley his brother is in town (before mentioning it was a "twin" brother who Jack made up), Mr. Furley gave a puzzled look and said "Your brother?" which appeared as if he didn't know Jack had a brother. However, in the previous season, Mr. Furley briefly met Jack's brother Lee, so he already should have known Jack had a brother (even if were to turn out to be a different brother).
Three's Company (1977)
1 character mistake in Double Trouble - chronological order
Starring: John Ritter, Don Knotts, Suzanne Somers, Joyce DeWitt, Richard Kline
Genres: Comedy
Continuity mistake: When Mr. Roper tries to explain to the girls and his wife what he was doing in Jack's bedroom, watch over Mr. Roper's left shoulder on the shelf. The number of yellow cans on the shelf keep alternating between one and two cans throughout several minutes. In addition, also notice the suitcase on the floor under the shelf as well. Whenever one yellow can is shown, the suitcase is by itself and whenever two yellow cans are shown, there is a square silver bag in front of the suitcase.
Ralph Furley: Ohhhh, I'm through with women.
Jack Tripper: Aww.
Ralph Furley: Don't you get any ideas.
Trivia: Once the first season with Terri started, Cindy no longer had "Snow" mentioned as her last name for the remainder of the episodes she was in (possibly due to the fact that this was the first season that started without Suzanne Somers completely and the producers wanted to retire the "Snow" surname altogether).
Question: During the first three seasons, all the main cast appeared in every episode (except one without Joyce Dewitt by season 3), but it seems once Suzanne Somers left the show, episodes had some cast members absent on a regular basis (mainly Richard Kline and Don Knotts who both only appeared in selected episodes in the later seasons). Was it a sudden budget cut or another reason for this?
Answer: Richard Kline and Don Knotts were supporting cast members, who could be replaced at anytime. It was John Ritter, Joyce DeWitt and Suzanne Somers who were the star vehicles they relied on to carry the show.