Upon learning that the book is about Frasier's first time, Martin asks if the book is about the night that Frasier and Lillith conceived their son (implying a belief that Frasier never slept with a woman, prior to Lillith). Lillith was Frasier's second wife. Martin seemingly forgets about Frasier's first wife, Nanette Guzman.
Several shots in the broadcasting booth were made through the partition, and show reflections in the glass.
At 10:23, when Frasier is yelling at Thomas in the booth, the lens on the camera filming Kelsey Grammer reflects the face of a woman in the studio.
Daphne, who is established in the series as still using British slang, threatens to smack Eddie on his "fanny" if he continues to disrupt Martin's therapy. While "fanny" is slang for the buttocks in American English, it's slang for the vagina in British English, making it a very strange thing for Daphne to say.
Eddie keeps interfering when Marty is doing his exercises. Daphne exclaims, "if someone doesn't let us get on with [the exercises], he's going to get a little spank on his fanny." In the US 'fanny' is a neutral word for a person's backside, but in the UK (where Daphne is from) it's an offensive term for the female genitalia. Daphne would be much more likely to use a neutral British English term, e.g. 'bottom' or 'bum'.