Well, the high school I attended in Grade 12 was on a penninsula that required a ferry to get to. From the ferry, their was only one road in, into town and to continue up the coast.
So just before the end of school we decided to "borrow" some detour signs, and on a long weekend when the ferry was packed, we detoured all the traffic up a street that ended up on an old logging road!
Of course the locals didn't fall for it, but the tourist traffic and most of the heavy trucks sure did! It's too bad there was no place to turn around once you got to the end of the road!
It took police and city crews about 6 hours to get it straightened out. Lot's of fun!