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: Martin is listening to Donny talk to Niles in his office. At one point Marty has his right hand up to his face but in the next shot his hands are laced together, resting on his stomach, with no time for a natural change. (00:09:30)
Continuity mistake: Frasier goes into the kitchen to get Niles some water; he gets an empty glass goblet, then opens the fridge and takes out a bottle of water and then it cuts to the glass sitting on the counter already full of water.
Continuity mistake: When Frasier and Niles are in Donny's office, in some shots his towel is next to his briefcase, in others it is on top of the briefcase. (00:04:40)
Continuity mistake: Donny is preparing Frasier for court and has a pencil in his hand which goes from eraser side up to lead side up and back again, from shot to shot, without him changing it. (00:08:30)
Revealing mistake: After Donny puts the phone onto speaker you can see him deliberately wiping the mustard from the sandwich across his left cheek to prepare for the gag at the end of the scene. (00:06:45)
Chosen answer: The turkey's stuffing.