The last episode broadcast to have been based on a novel by Erle Stanley Gardner.
Peggy/Ethel looks up Perry Mason's phone number in a Los Angeles phone book. His number is MA 5-1190.
This is based on the same premise as the season two show "The Case of the Foot-Loose Doll".
This episode (and at least one other) features an instrumental of the song "You Need Us," which was sung by the Honeybees on Don't Bug the Mosquitoes (1965).
The background music playing while Peggy Sutton is on the phone is practically the same as the song from Gilligan's Island, "You Need Me," sung by The Honeybees.