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Louis Jourdan, who plays the critic, is French. Antony Alda, who plays the Italian-speaking nephew, is also French. The actor playing the chef gifting Columbo with a plate of mushrooms, despite doing his best to speak English with a French accent, is not.
One of the few episodes where Columbo admits to disliking the murderer.
Antony Alda (the younger half-brother of actor/director Alan Alda) plays the Italian-only speaking waiter.
Although Mrs. Columbo never actually appears, Mrs. Falk is in this episode (and five others as well). Shera Danese was married to Peter Falk, starting a month before this episode aired until his death in 2011.
The suspect, Paul Gerard, drives a Stutz Blackhawk, a rare early-1970s American car. It was a status symbol that demonstrated affluence far beyond that of even Rolls-Royce or Bentley.