The boarding house interview scene with Mike Lally was filmed several months after principal photography was completed on the episode. The writers hadn't completed, or could not agree on, the plot twist featuring Lally as a damning witness who could help to reveal Santini's true identity. Peter Falk himself wrote and directed the scene. Lally had appeared in 20 previous episodes of Columbo in minor roles or as an extra, making him the second-most cast actor of the show behind Falk. Lally's son said the scene, which uses Lally's real name for his character, was Falk's gift to the elderly Mike Lally for his otherwise nameless contributions to the series.
Jack Cassidy was one of few actors to make repeat appearances in Columbo, guest starring in three unrelated episodes as the murderer. (The others were Murder by the Book (1971) and Publish or Perish (1974).) This episode was Jack's third and final appearance on Columbo. He died December 12, 1976 at age 49.
The song being crooned by Santini's daughter's love interest at the start of the show is the theme song for Charade (1963).
Bob Dishy returns as John J. Wilson, who is a younger detective that goes more by the book than by Columbo's hunches, showing the difference between a common lawman and the titular genius.
Peter Falk may have an artificial eye, but not Columbo. When he says, "You can see it!", he points to his non working eye.