From Forgotten Lady when Columbo is being questioned by the other officer about not seeing him in the Homicide Office, and Columbo’s response is “well I don’t get down there too much, none of the murders take place there you know”. I love his subtle sarcasm!
In Trace of Murder, a great in-joke by Peter Falk. Columbo wants the forensic tech/murderer Patrick to meet with co-murderer Mrs. Calvert so they can "get a good look at her". Columbo says, "You and me together, Patrick. Three eyes are better than one."