Continuity mistake: Niles and Frasier meet Donny for the first time in his office. Donny's secretary brings him a sandwich and he takes a bite out of it, in the center of the sandwich half. He starts saying how good it is, and offers the guys a bite - now the bitten part has moved and is on the outer edge of the sandwich.
Continuity mistake: When Frazier comes into his booth to begin his show, Roz is reading a book. She says "Happy Birthday" to him and we can still see the book in front of her; but in the next shot it is lying on the console next to her, without any time for her to have put it there.
Continuity mistake: Early in the show Frasier finds Daphne's engagement ring which she had misplaced. He is holding it - on the table we can see a chip bag that Daphne had used to hide her ringless hand. During the course of the scene, the chip bag appears and disappears several times.
Continuity mistake: Frazier meets his date (Cassandra) in the restaurant - she places her purse down, and it constantly moves around in different positions while they talk. Sometimes it's to her right, sometimes to her left, and one it is lying on the table with her hand over it.
Continuity mistake: Near the end of the show, when Niles, Frasier, and Martin are at Duke's, Niles says, "I'm not here just for you, Dad" and he puts his hand on Marty's shoulder. The next shot shows him standing about two feet away, with his hands by his side. (00:21:20)
Continuity mistake: Frasier is sitting on his couch with Poppy, dropping hints about having an arts show on KACL - she has her hands folded on her knee. As Daphne says "he means your mother", the shot changes, and Poppy is suddenly holding a glass of wine, with no time for this to have happened.
Continuity mistake: Similar errors occur in two different scenes: in the first breakfast scene, the coffee pot is sitting on the table but in the next shot Daphne is pouring herself a cup, with no time for her to have naturally picked it up. Later in another scene, Niles is there for breakfast, picks up the pot, and pours himself some coffee. In the next shot, the pot is on the table, again without enough time for him to have put it back.