Continuity mistake: Niles is at Frasier's apartment, visiting with Marty. He takes some crackers out of his black fanny pack and puts the fanny pack behind him. We see it there when he stands up but there is a shot where there is nothing on the couch behind him. It then goes back to showing the fanny pack.
Revealing mistake: In the scene where Frasier and Lilith meet in the living room, where Frederick has created a romantic atmosphere, Frasier has a long speech about how Lilith is not going to get him back, ending with "I need to be finessed!" and Bebe Neuwirth goes out of character and begins to giggle, before she quickly covers her mouth and pulls herself together. Though Lilith might have found Frasier's comment amusing, it would definitely not be in character for her to giggle like that.littlestar
Revealing mistake: Frasier comes in complaining how workmen in the service elevator have dribbled chili dog on his foot. He is holding out his shoe saying "How ever will I get that stain out", and Eddie runs over and starts licking what we think is the shoe. Frasier makes a comment about dog saliva being the universal solvent. In fact, Eddie does not even touch the shoe, but licks the floor in front of Frasier. Obviously the floor was treated with something Eddie would enjoy licking up.
Continuity mistake: Abbie and the gang are in the restaurant for dinner. Frasier has his elbow on the table over his menu and Abbie says, "In front of your father," and the camera angle now shows Frasier holding the menu. After Abbie responds to Marty's lawyer joke, Frasier's hand is back down on top of the menu.
Continuity mistake: When Abbie arrives at Frasier's apartment, she puts her purse on the coffee table; the strap is hanging between the couch and the table. When Frasier offers to walk her to the elevator, she goes to get her purse and it has flipped over with the strap fully visible - even though no one went near it.
Continuity mistake: The gang is reading through the script and Roz cues Bulldog and as she does we can see Gil has his script opened up on his knee. As the shot goes to Bulldog, Gil's script is now folded over and his pencil is in his right hand. He wouldn't have had time to change position.
Continuity mistake: When Frasier and Martin are leaving Artie's hospital room, Frasier has the door about one-third open. Just before they leave, though, as Frasier says "next time he'll stay longer", the door is open much wider. Nobody opened it wider during that time. (00:08:50)
Continuity mistake: Donny is sitting on Frasier's couch eating Chinese food. One of the containers, with chopsticks in it, is sitting on the table, near the center. In the next shot the chopsticks have disappeared and the container has moved towards the end of the table. (00:12:05)
Continuity mistake: Quite late in the show, Nikos and Frasier are sitting down talking. Behind Nikos someone picks up a glass of wine which is next to a bottle. The next shot shows a plate there as well, even though no one put one down. It disappears a couple of shots later - again, no one went near it.
Continuity mistake: Roz and Frasier are at Cafe Nervosa and she is telling him about her dream of dancing with Bruce Springsteen. At one point, her hand is on top of her coffee mug and then she lays it on the table; the next shot shows her hand on the cup again, with no time to move it naturally.