The name of the upscale day spa that Frasier and Niles visit is aptly named La Porte D'argent, which is French for "The Silver Door." Furthermore, "argent" also means "money" in French.
The spa's security is not as efficient as it is originally presented. Frasier (Kelsey Grammer) gains entry to the spa by calling Niles (David Hyde Pierce) "Cam Winston," whose invitation they have and whose name is on "the list." However, Frasier frequently calls Niles by his real name within earshot of the spa's staff. That should have blown his cover, but it didn't.
When Daphne tries to tempt Martin into watching [link=tt0071042 again, she says it's a good one because Tom Selleck is in it. Selleck really did appear on Rockford, twice, as a charming private investigator, which helped him land the breakout role of Magnum on Magnum, P.I. (1980).