During a training session when I worked in the motor insurance business, someone enquired if 'registration' and 'registration mark' were the same thing. The trainer's disdainful expression was a corker. In fairness to our enquirer, he has come a long way and is now MD of a large commercial insurance broker.
I think one daft question we will all have heard at some time or other is,
'Excuse me, do you have the right time?'
'No, but I have the wrong time if that's any use.'