I'm going to join in quick as this one's pretty easy...
When I was about 13/14 I went on a school trip to Italy. It was a Catholic school so of course we were forced to go to church on Sunday.
So here we are. The church is like a hole in the wall but huge, packed out and we all sit near the back as the 'outsiders'. this place is also FULL of gold. No cheapo candle sticks or light fittings here..
Our teachers also force us to take communion, which is embarrassing at the best of times. I'm up for getting that done quick with as little fuss as possible. Body and blood of Christ and all that, while holding the communion plate at our chest so no Jesus crumbs fall onto the floor.
As I'm walking back to my seat I see my geography teacher with his head in his hands. Only then do I realise I've accidentally done a runner with the huge solid gold communion plate!
Aside from that, a few times I've been DjIng and picked up the wrong stylus but that's easily done. Less so playing from CD but I've also managed to eject the wrong one of those...