When Bulldog calls Frasier at home to get him to sing "Three Little Maids" from "The Mikado," Frasier's phone has a cord attached from the handset to the dialer. Up to this point (and afterward), his phone has always been cordless.
Lizards have weak jaw muscles, and no species of lizard sold in a pet store would be capable of biting off the finger of a woman (i.e., the unfortunate Kate).
About 3:30 into the show, while Kate and Fraiser are walking down the hall at KACL you see the shadow of the camera being used tracking before them.
When Kate is about to enter a sound booth to fire someone, as she is talking to Frasier, the microphone (or its shadow) is visible above her head.
Niles refers to an exhibition of "netsuke" and mispronounces it "net-SOO-kay" (Frasier doesn't correct him). But the erudite Drs. Crane would surely know that the correct pronunciation puts the emphasis on the first syllable, almost elides the second, and softens the vowel of the third: NETS-(ih)-keh.