My maths teacher got the whole class to believe that we were changing to euro tax of 10% next year, then the year after they're changing everything to euro time, 100 seconds in a minute, 100 minutes in an hour and 10 hours in a day. I was confused as f**k, but it was the most unexpected piece of awesome. He's an old man, ffs! EDIT: kept us going for an hour, and then we all went off confused as f**k trying to persuade everyone else it was happening