Two friends of mine were getting married. I found a plastic goose that honked when it detected movement, turned it on, wrapped it up, and slipped it in with the rest of the wedding presents.

Alas I was not there, when they unwrapped their gifts and found that one of their presents was honking at them while they unwrapped it. But I gather they were rather more than nonplussed.

My mom would have killed me if I'd pulled that prank with the police!