Columbo says that line to Ralph Dobbs after telling him about his wife's vacuum cleaner causing static on the TV and so on. Then he says that if he does find it boring, he can go ahead and answer his questions.
My question is, is this the only time he admits that his small talk is part of a plan? I can't think of any other times.

hmmmm ... Another occasion might be when Columbo so-matter-of-factly blurts out to Leslie [after scolding Margaret over the keys] ... "I mean, I just can’t have you accused of murder on the wrong evidence."