Continuity mistake: Frasier is having a glass of sherry, sitting on his couch, talking to Niles and Martin. As Marty says "let's go have dinner", Frasier throws his hands up - in real life he would have still had the sherry in his hands. There was no time for him to have put it down.
Continuity mistake: When Manu pulls down the metal front over his kiosk, Frasier has his umbrella in his right hand. By the time Manu pulls it all the way down and catches his hand under it, Frasier's umbrella has shifted to his left hand, even though he never transferred it.
Continuity mistake: The shot after Roz says "Roz Doyle, radio producer, single" shows the guy nearest to the window in the other room with his left hand next to his mouth and the woman next to him with her hand next to her chin. The following shot shows the man closest to the window with both his hands next to his mouth and the woman sitting next to him with her hands on her lap.