When I was in sixth form, there was one computer where the mouse wasn't working.
I looked at it briefly, realised that the cleaners had unplugged it and bent a pin when re-inserting it (it was a 9 pin serial mouse).
Teacher looked over and saw I'd got the connector in my hand and asked what the problem was. He said "just get another one out of the cupboard", by which time I'd already got my multi-tool pliers out of my pocket and straightened the pin... "No, it's alright, I've fixed it already"