Of course, it wasn't intended to be, but "A Case of Immunity" tickles me throughout.

"How most astute Alafa..." HAHAHAHAHAHAHAHA

I have to agree, "Negative Reaction"
was the best. Don't forget about the
scene where he asks Galesko for
a pin-up for his dog, and the horrible
photos taken at the funeral.

I've mentioned this before (a couple of times I think)- THE funniest scene ever is not performed by Columbo himself, but a murderer. In "Columbo Goes to College" one of the killers does a dead-on impersonation of Columbo ("You know what I gotta do - I gotta go see the coach's wife!!") ANY Columbo fan will smile ear-to-ear no matter how many times you've seen it.