The "soothing" DVD that Niles chooses at Frasier's is The Mikado (1939).
Frasier mentions several times that he and Julia have dinner reservations at Chez Henri. However, he was banned from the restaurant in the Season 9 finale, "Moons Over Seattle". It's possible that he made peace with the owner but highly unlikely.
Many times characters say that Frasier and Roz slept together "two years ago," but in fact, it was only one year ago.
Nurse: Hi. I'll get you a cup and you can start...
Niles: No, no. I've already donated my essence to your establishment, now I'd like to get it back.
Nurse: I'm sorry. It's against our policy to return essences.
(Both Niles and Daphne are looking at the results of a home pregnancy test)
Niles: We're pregnant.
Daphne: Oh, my God, we are, aren't we?
Niles: But my slow sperm...
Daphne: (After deliberating a moment) I must have fast eggs!
(Frasier and Roz are discussing the night they slept together)
Frasier: I don't remember you having any compaints when we were in bed. I seem to recall hearing the term "stallion-like".
Roz: I never said that.
Frasier: Well, one of us did!
(Frasier thinks that Roz was in love with him and that her feelings began when they slept together)
Roz: You have quite the ego on you. We slept together like two years ago. I mean what do you think you are, some kind of slow acting, time release love bomb?
Title: No Sex Please, We're Skittish
The episode title is a reference to the 1973 Comedy "No Sex Please: We're British".