Wilson received a paintball gun as a gift at Christmas (10) and when he tired of shooting trees and other stationery objects, he called on neighbour Harrelson to help him come up with a more dangerous game.
He explains, "I only got one (gun) and there's only so long you can shoot at the trees and stuff... What we came up with... we were playing dominoes and the loser had to run from the other guy - the other guy got, like, 20 yards away and he ran from the corner of the house, touched the tree...
"It started where you could kinda put on a jacket... but we were like, 'The welts aren't that bad when it's like that.' Then we reduced it to, you could just wear your shorts, and that was it."
Wilson aired video footage of the two pals playing the painful new game, and arguing about the number of shots fired, on Thursday night's (24Jan11) Jimmy Kimmel Live! in America.