Continuity mistake: When Niles and Daphne are talking at Frasier's door, Daphne says "Now poor Roz really is in that predicament" and her arms are in front of her with her hands clasped. Niles says, "Do I smell chicken?" and immediately her arms are crossed, without enough time for her to change position.
Continuity mistake: After Rick has left Roz's apartment, she goes into the kitchen with the roses and just as she gets there Frasier knocks on the door. Within a couple of seconds she comes back with the roses in a vase, but she just didn't have enough time to do this in "real time".