Visible crew/equipment: When Frasier is standing through his sunroof to speak with the drivers stuck behind him in the parking garage, one shot shows Frasier's body and much of the rear window which features a very clear reflection of the boom mic.
Continuity mistake: When Grace is talking to Quentin's teacher she erases some letters from the chalkboard. For the rest of the scene the amount that is erased keeps changing.