Continuity mistake: At the end of the episode after Sam mentions stewardesses he claps his hands, and his seat belt (which was caught on something) moves across his chest to the regular position. Cut to a wide shot of the car and Sam's seat belt is back to the position it was in before.
Continuity mistake: About two thirds of the way through the show, Marty and Frasier are talking in the living room. Marty is sitting in his chair with a glass of milk. One shot shows him with both hands on his milk, and then he puts his left hand on the arm of the chair. In the next shot his hands are around his glass of milk again.
Other mistake: When Frasier is complaining that he is not mentioned in the acknowledgments of the novel, he picks up the book and then slams it down on the desk. It sits face up, near the front of the desk. In the next shot of the desk, we see that the book is face down and has moved back.