Splanking
From Glitch Strategy
Splanking is the act of hitting another player with a Plank.
With a Plank in your inventory, you can "splank" other players with it, similar to a hug or an kiss. Click on the player and select "splank" while having a Plank in your inventory. You lose 10 energy from doing this and the receiver of the splank loses mood. There is an achievement for splanking 23 players: Hanky Splanky. You do not lose the Plank when you splank someone.