Get a guirrila (sp?) suit on and walk in front of a trail cam. He will think he got a picture of Sasquatch. We did this, and he spit out his beer he was so surprised. At first he didnt believe his eyes, but we pretended to be surprised also and he was scared to go walking in the woods in the dark!

ps - and you HAVE to make sure there are no hunters in the woods at the time you do it