I'm surprised there aren't more posts on this topic...ad libs.
I was going to ask the question...listing the tomato/tie scene as MY example...of an ad lib for sure
another I think is in Publish or Perish when Columbo has a hard time getting up after eating the chili in the restaurant ...seems like an ad lib.

any more folks?

I get the feeling where he breaks his shoelace in Exercise might have been unscripted.

in "Murder by the Book", the script has Falk saying the secret to a good omelet is "no milk, just eggs." In the actual show, he says "no eggs, just milk". It's either a flubbed line, or an ad-lib, I don't know which.

I heard Peter talk about this one......In "Any Old Port" Peter was on the phone waiting on hold and started whistling This Old Man, that one was an ad lib, it stuck and sort of became an unofficial theme.