I'm not sure if this would exactly qualify as "fast food", but in both "The Most Crucial Game" and "The Bye Bye Sky High I.Q. Murder Case" Columbo eats ice cream from a vendor. In both instances he has positive reactions. I especially love in "Most Crucial" how he irritates Robert Culp by saying how good the ice cream is, rather than getting to the point of his visit.

I just recalled another instance, in "Murder by the Book", where Columbo is questioning the man about Jim and Ken's insurance policy while eating at one of those hot dog stands shaped like a hot dog. Columbo seems a bit preoccupied with getting information about the case, so (if I'm remembering right) he shows little reaction, except perhaps a sense that this is a fairly typical meal for him, nothing different or out of the ordinary.

I always like the line in that scene where he asks for a receipt (since it's on his expense account). I do the same with a bank card, even if it's something tiny from the convenience store.

At the end of EXERCISE IN FATALITY, Milo sarcastically calls Columbo's evidence "cigar ashes." It just occurred to me, but Marshall does his best to make that LITERAL.

I'm sorry, I of course meant to put that last remark in the MIND OVER MAYHEM thread.