During the cafe scene Roz asks Clint if he can speak French, Clint replies "seulement quand je rencontre une belle femme" Translated to English he's saying "Only when I see a beautiful woman"
When Niles (David Hyde Pierce) asks about "Swiss prosciutto," the shopkeeper reiterates with the correct name "Bündnerfleisch." The Italian term "prosciutto" was probably chosen by the writers for the benefit of the American audience in order to give viewers a point of reference - prosciutto is widely available in the States and the process of making it is relatively well-known. There are a few other notable differences between prosciutto and Bündnerfleisch, some of which are: 1) prosciutto is made from pork, Bündnerfleisch from beef; 2) Bündnerfleisch undergoes several weeks of maceration before being air-dried, prosciutto is salted, pressed, and then air-dried; 3) although travelers are prohibited from bringing either type of meat into the US, prosciutto is commonly imported into the US, Bündnerfleisch rarely is. This helps to explain Niles's excitement at the prospect of buying it in the shop.
The celebrity caller in this episode is Jill Clayburgh (Marie) who has a hard time getting out of bed every morning, and that she feels irritable when she does.
Frasier no longer uses his antique French chess set he bought in Chess Pains (1996)
The song Clint sings at Frasier's party, "Isn't It Romantic?", was written by Lorenz Hart and Richard Rodgers. It was first introduced in the 1932 film "Love Me Tonight," starring Maurice Chevalier and Jeanette MacDonald, and has since become a jazz standard and a part of the Great American Songbook.