Genius from B3ta.com

  "Driving my cousin home one Friday
  night we passed a group of boys walking
  into town. One of them drew our attention as he
  was dancing like a tit, with his pals laughing.
  Unbeknownst to him, as he was doing this, his
  wallet fell out his back pocket. 
  My cousin suggested we turn around and see what was 

  in it.
  By the time we got there, the boys were nowhere
  to be seen and the area was deserted. After some
  searching we found the wallet which contained
  just 20 pounds, cards and a ticket to a gig that
  night. 
  We decided to find the boys and give it
  back, laughing at how surprised he would be to
  be approached and handed his own wallet. But
  then a much funnier idea came to us. First we
  drove around until we spotted them. Then,
  knowing they were heading in to town through a
  quiet industrial area, we drove about a quarter
  of a mile ahead. 
  We then placed the wallet on the pavement 
  right in their path and hid to watch them approach, 
  say 'Hey! That's someone's wallet over there,' 
  walk up to it, pick it up excitedly, open it looking for riches 
  and inexplicably discover it was theirs. The
  absolute confusion and surprise was hilarious to
  watch. I like to think they still talk about how
  one of their wallets somehow jumped ahead of
  them."