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: In the opening scene, Roz and Frasier are in Cafe Nervosa, and she is snoozing, while a half-eaten muffin sits in front her. As she wakes up and talks to Frasier, the muffin appears whole again. She leaves and Martin comes in and takes her seat. A shot then shows the muffin as half-eaten again, even though no one has touched it.