The shot of Rocky's truck riding up the hill toward the Mobil station is stock footage from Profit and Loss, Part 1: Profit (1974) from season one. It is also used at the beginning of Beamer's Last Case (1977) from season four.
Character actress Fritzi Burr makes her annual appearance in this episode. She plays the clerk at the vet clinic, to whom Jim chats with, trying to track down the ephemeral 'phantom-lady Odette Sorrell'. Ms. Burr appears in one episode-per-season, usually playing a tart-tongued employee, with a terrific 'poker-face', but, here she's (comparatively speaking) ebullient.
When Marv's explaining to Rockford how he got arrested he mentions his client's ex is a freak and spends his Christmases at "Camarillo". This must be a reference to the now defunct Camarillo State Hospital in Ventura County. The grounds of the former hospital is now California State University Channel Islands.
The Waterbury Building was known as MCA Building. It was designed in 1963 by Ralph Vaughn. Following his takeover of the studio, Edgar Bronfman renamed it in 'honor' of Lew Wasserman, head of MCA. It was subsequently torn down, and a new, 35-storey tower (10'Universal City Plaza, 10UCP), designed by designed by Skidmore, Owings & Merrill.