Roz comes over to Frasier's apartment to stay in Martin's room while he's away in San Francisco, but throughout the show she comes and goes only from Daphne's room.
According to the dialogue, Martin was still in the Marine Corps as of 1952. This conflicts with the fact that earlier episodes establish Frasier as having been born the same year; it defies belief that Martin could get his discharge (in wartime!), be hired by the Seattle Police Department, graduate from the academy, meet Hester and sire Frasier all in the first three months of 1952.
This episode is supposedly set on the fifth anniversary of Daphne's employment with the Cranes. The episode in which they hired Daphne was broadcast four years and eight months earlier.
When Daphne, Niles and Martin all go into the kitchen to laugh, Daphne takes something out of the hot oven. She wears an oven mitt on her right hand, but then also puts her bare left hand onto the hot dish and leaves it there before setting it down on the counter.
(At 00:04:26 and 00:11:40) It's obvious that Martin's holdall is empty.
(At 00:11:00) Jordan Baker, who plays Paula Garrett, struggles to contain her laughter when she says "We have two giant schnauzers".