Continuity mistake: Frasier is on the phone at KACL with Jerome's girlfriend and the reflection in the glass shows him raising his hand to his face, but the next shot returns to him - his hand is on the console. There was no time for him to have shifted positions normally.
Continuity mistake: When Frasier is in the boardroom with Roz and her production team, Frasier is writing in a binder, which is on top of a couple of books. In some shots we see a couple of different books in front of him on the table. One of them is called "Mars," which he had put back in his briefcase at the beginning of the scene.
Continuity mistake: Near the end of the show, Dr. Nora's mother is chasing Nora through the corridors of KACL, behind the windows of Frasier and Roz's booth. We can see them go by, from window to window. The shot then cuts to Frasier, looking horrified, and we see Nora's mother run by a couple of windows again - even though this could not possibly have happened in real time.
Continuity mistake: When Frasier and Niles are in the restaurant, Niles is under the influence of medication. He lays his head down on his arm just as one of the geniuses arrives and greets them. In the next shot, his head is lying right on the table, with no time for him to have switched positions.
Continuity mistake: When Niles is engaged in his ironing fiasco, Eddie is watching his every move. When Niles heads to the kitchen to get spot remover, Eddie is sitting on the footstool. The next shot shows Eddie turned to watch Niles - but he is now in the chair; it is not just a tricky angle, as he actually lays his chin on the back of the chair. There was no time for Eddie to jump from the footstool to the chair.
Continuity mistake: When Daphne goes to Niles's place to see him, she sits down on the couch and slides her purse behind her. A couple of shots later Niles gets up and now we can see her purse on the couch to her left. At no time did she make any movements that could explain its change of position.
Continuity mistake: When Marty, Niles, and Frazier return from the taping of the Antiques Road Show, Marty hangs up his blue windbreaker and then Frazier hangs up his gray raincoat, obscuring Marty's coat. But throughout the scene, all we see is Marty's blue jacket - where did the raincoat go?
Continuity mistake: At the end of the show, when Martin, Niles, and Frasier are leaving Niles's place to go out for ice cream, they leave Maris's opened package on a large footstool next to a decorative metal bowl. When they return (closing credits) with their ice cream the package and its wrappings are gone - even though no one was left behind in the apartment.
Continuity mistake: During the opening scene, Niles is on the phone to his chef, and behind him, on a table, are two champagne glasses (beside the phone base)and 3 candles. He hangs up the phone, moves away and 2 of the candles and the glasses have disappeared, and the phone has been pushed further over. He sits on the couch, then goes to get the ironing board - when he sets it up we see the glasses and candles are back.
Continuity mistake: Throughout the Christmas parade we can see that the headphone/microphone is on the left side of Frasier's head. During the first break just after one of the crew members is telling Mary that her improv is really good he tells Frasier to lighten up. Just after he says this you can see that the headphone/microphone is now on the right side of Frasier.