As having served in the role of producer for many episodes, it's a chance for Henry Winkler to make an appearance as Wilton Newberry, the uncredited role of the Attorney for Harry's will.
Marion Ramsey from Police Academy (1984) makes a guest appearance at 13:49, dressed as a police officer.
Henry Winkler and Marion Ross of Happy Days (1974) fame both make guest appearances. Winkler plays the attorney while Ross plays Sister Robin.
The classic car is a Nomad. Guest star James Doohan's Star Trek (1966) character "Scotty" was killed (and resurrected) by a machine named "Nomad" in The Changeling (1967).
Wendy O. Williams guest stars as Big Mama. Williams was the lead singer of the infamous punk band The Plasmatics, a stripper and starred in adult films. She attempted suicide two times before her final, sadly successful, attempt in 1998.