Continuity mistake: Just before Marty says "Quack" to Daphne, his hands are in his lap. The next shot shows them on the arms of his chair. (00:05:40)
Continuity mistake: After Frasier is left alone in the apartment, we can see a glass of sherry and a can of beer on the coffee table, but neither item was on the table when he was talking to the others before they left the apartment. Roz's purse also shifted from the couch to the little glass table during the shot change. (00:21:20)
Continuity mistake: There is a bag of chips on Marty's little table that goes from being open but almost flat to being open much wider and the bag is very rounded, from one shot to another, but no one touches it. (00:18:05)
Continuity mistake: After Frasier passes the pink box with the birthday cake over to Daphne the box is closed. But when the doorbell rings the lid is about halfway open, with no time for this change. (00:04:15)
Continuity mistake: Just before Frasier says "What I want is to be left alone", Roz, Niles, Marty, and Daphne are standing at the door. The shot goes to Frasier, and then back to them, and they have all changed positions, with no time to have done this naturally. (00:21:25)
Answer: Nanny G (Nanette Guzman - played by Laurie Metcaf) has been a children's entertainer for twenty years, and tells Frasier, "Do you know what it's like to play the same character for 20 years?!" The joke is that Kelsey Grammer has been playing Frasier Crane since 1984, when the character first appeared on "Cheers", so Kelsey in real life has been doing just that!
Super Grover ★