Continuity mistake: While Marty and Frasier are fighting Marty smashes some plates. The shot changes to the living room with Frasier apologizing and then switches back again. However, now all the smashed crockery has disappeared to be replaced by what looks to be a bowl and a tumbler.
Continuity mistake: As Frasier pushes Sherry towards the balcony, we can see a gold decorative thing on her green purse. In previous shots to this, the gold piece didn't show, because the other side of her purse was facing out. At no time did she turn the purse around.
Continuity mistake: Niles and Frasier have drugged the rottweilers with some of Maris' pills and Frasier points towards the french doors and says, "The dogs are getting drowsy." We see the dogs dropping to the ground. The next shot of the doors, a couple of seconds later, shows no sign of the dogs, although they were visible from that angle just before that.
Continuity mistake: While Frasier and Marty are in the kitchen arguing about Sherry, his can of beer moves from the right side of the counter quite a distance over to the left of the dishes he broke. The sugar bowl and jam pot also change positions during the same shots.
Continuity mistake: Frasier's third date, Leslie, shows up at his apartment wearing a long off-white coat. He hangs it up beside the fireplace; for the rest of the scene we sometimes see the coat hanging with the left sleeve straight and sometimes with the left sleeve all crinkled up.