Good concept, Martin! Very clever. It does seems little odd that a show lasting as long as "Columbo" never got around to doing a "Christmas episode" -- that I recall. Some shows, it seems, can't get through even the first season withoout doiing a parody of "A Christmas Carol".
I'm not good at matching characters with actual seasonings, but for Robert Conrad's Milo Janus it could be something health-conscious. And for Louis Jourdan's Paul Gerard and Martin Landau's Dexter Paris it could be almost the opposite, something as extravagant as possible.
Laura got the Van D*** and Albert answers, quid quo pro the Gordon solution.
Of the remaining, the Cassidy clue is in his coolly villainous name, Landau's one-time partner was a spicy spy, and Harvey's Russian chessmaster gave him a fair "shake," putting him in a black mood.
Yes, very odd, especially given Columbo's rather elfish nature. Betting the monthly nature and uncertain scheduling of the Columbo installments forced the network to avoid any seasonal elements.
Wouldn't Sebastian Cabot or Orson Welles have made a wonderful '70s-era villain, using his stowed Santa suit as a Chesterton's postman device to escape notice during a department store or office Christmas Party murder?
Have a wonderful New Year, if you haven't already. I may block out tomorrow entirely for the NY Columbo Marathon on MeTV...
Nailed the Dick Van D*** and Eddie Albert answers! Great guess on Jack Cassidy, though I was going somewhere else. More clues: The Cassidy clue is in his villainous name, Landau's one-time partner was a spicy spy, and Harvey's Russian chessmaster gave him a fair "shake."