Columbo shows his innocent school boy mindset in Etude in Black.
When he goes to Audry's ballet lesson she comes over to him and he says,"Audry I'm very impressed with you. and She says, "Oh really is it my body or my mind"? And Columbo says, "Well it's both really". What a thing to say to a twelve year old! It was very funny.
I think this was improvised by Peter, he almost starts laughing and Audry looks surprised at the line, she smiles and doesn't look like she is expecting him to say that, and almost loses the scene but Peter keeps it going. It doesn't look scripted to me. With Cassavetes on the set I'm always looking for improv in this episode.
It could be included in a current show, but probably only if it came from some one-time character instead of a main character, and with some "PSA" kind of stuff attached to it, and so on, probably ruining the whole effect of the little joke!