The house used as the Lefcourt's residence was also used as Bob Coleman's estate in the earlier episode, The Deep Blue Sleep (1975).
The reason Jim seems familiar with stock trader Jeff Cooperman is because he's supposed to be Norm Mitchell (Tom Rosqui), who Rockford met in Profit and Loss, Part 2: Loss (1974). Unfortunately, Mr Rosqui wasn't available, so a similar-looking actor (Tom Bower) - using a different name (shot in the same place) was used.
Warren's blue AMC Pacer was originally painted red. The red door jambs are visible when Warren leaves the car with the valet at the wedding.
"Nine to Five" was also filmed at the Bellagio address.