Continuity mistake: Frasier is off to find Niles and he tells Martin to come with him. Marty puts his chair down as he says "I don't want to go to Niles'" - the shot changes and we see him lower the chair again. His coat in his lap also changes position between these two shots. (00:17:40)
Continuity mistake: Marie and Frasier are sitting on the couch when Marty comes home, and her arms noticeably change position as the shot changes. Then, a few shots later, she has her hands on her legs above her knees, but in one quick shot her hands are wrapped around her knees - without enough time for her to have changed naturally.
Continuity mistake: Frasier comes home to his apartment with a bottle of wine in a paper bag. He takes the bottle out and puts it on the table holding the bag in the other hand, but in the next shot we see the bag is already on the table and he is just placing the bottle down.
Continuity mistake: At the picnic, Bulldog puts his hand on the shoulder of a little girl in a dark pink dress, just before the pinata bashing starts; the next shot shows the same little girl is standing on the other side of the pinata, next to a woman in a blue and white striped top.
Continuity mistake: Marty and Niles are getting off the elevator and Marty transfers his mail into his left hand just as he goes to open the door to Frasier's apartment. When the shot changes to show them coming into the apartment, the mail is in Marty's right hand - there is no way he could have transferred the mail again in such a short time.
Continuity mistake: At the end of the restaurant scene, where Frasier, Roz, Martin and Roz's mother are eating, Frasier puts his crumpled-up napkin on one side of his plate, but at the end of the scene it has mysteriously switched to the other side without being moved by anyone.
Continuity mistake: Marty, Frasier, Niles, and Daphne are in Frasier's apartment, talking about Marty moving in with Niles - M.'s beer can and remote are sitting on his little table. In one shot they are quite close together, but in the next the can has moved about six inches forward.