This episode was part of NBC's 75th anniversary celebration, in which actors from previous NBC shows guest starred in current ones.
After Norm (George Wendt) explains why Vera won't be attending the party, Frasier (Kelsey Grammer) tells Niles (David Hyde Pierce) that Vera is Norm's "much-storied" wife. It is highly appropriate that Niles be told about Vera since Niles's much-storied first wife Maris was never seen throughout the "Frasier" series -- as Vera was never seen throughout the run of "Cheers (1982)."
One of the guests at Cliff Clavin's (John Ratzenberger) retirement party appears to be director James Burrows, who directed 32 episodes of "Frasier" and 237 episodes of Cheers (1982).
L'Espalier, the restaurant Niles (David Hyde Pierce) has reservations for, was one of the most expensive and well-regarded restaurants in the country at the time this episode was broadcast. Unfortunately, the iconic restaurant closed on New Year's Eve at the end of 2018. This was one of the few occasions that a real restaurant name was used throughout the series.