The Case of the Wandering Widow - S4-E6
Character mistake: As Mr. Morgan (Dean Harens) is being examined by the prosecutor he's also sitting in the gallery.
Perry Mason (1957)
1 character mistake in season 4
Starring: Raymond Burr, Barbara Hale, Ray Collins, William Hopper
The Case of the Sausalito Sunrise - S9-E19
Revealing mistake: Secretary Della Street answers the telephone in Perry's office and speaks briefly with the owner of an art gallery. She presses the "hold" button, then hands the receiver to Perry and says, "It's Mr. Clune." Perry and Mr. Clune have a lengthy phone conversation, even though Della never released the "hold" button.
Hamilton Burger: Incompetent, irrelevant, and immaterial.