When someone starts laughing really hard and they feel the need to slap the nearest person. Then when the person got slapped asks why they did that, they say it's a joke.
Friend 1: omg that was so funny
Friend 2: hahahaha *slap*
Friend 1: ouch what was that for
Friend 2: chilllllllll it was a joke
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.