So I saw this on another website a few days ago and didn't have time to post it then.
A marketing student, who is about to graduate, set up a very interesting campaign for Burger King in Florida. Here is the page that I found, it has much more info and pics. But to sum it up, people walk around Orlando and "accidentally" drop their wallet. When someone pics it up and tries to give it back to them they say something along the lines of "Keep it, it's on the King". (The King being their mascot right now, I am sure you all have seen him super creepy). Inside is a bunch of Burger King money and other random joke items.
While I have not eaten at a Burger King in the past two years, and this does not make me want to, I still think it is a pretty effective ad campaign that could transform into an interesting performance piece with some tweaking.