In the sequence where Columbo inspects the soda glasses, they appear to be filled with ice-cream. Right after Columbo leaves, Alex Brady takes those glasses, intending to break them, but at that point they appear recently emptied. See more
[referring to the water bed
You know, I've never tried one of these. My wife, that's Mrs. Columbo, she tried to get me interested.
[after Columbo lies on the bed
Well, how do you like it?
Well, to tell you the truth, sir, it feels all swimmy. Makes me wonder what Mrs. Columbo had in mind.