Earlier this week Stephen Amell (Oliver Queen on Arrow) tweeted that he'd taught his baby daughter how to do the fist bump and blow it up thing. This gif is Willa Holland, who plays Thea on the show, demonstrating for us. I may die of the cute. OMG.
Original fist bump: Legolas tried to punch Gimli at the same time that Gimli tried to punch Legolas. They hit eachother's fists and got distracted from being mad at each other by the super awesome thing they just came up with. Well that's my theory anyway =)