Monday night on The Tonight Show, John Stamos and Jimmy Fallon played a game of "Kid Dictionary." Parents sent in videos of their kids defining words, and it was up to John and Jimmy to guess what the F the children were trying to define. Stamos is famous for being a cool uncle to kids on TV, and Fallon is a professional child (right down to the clumsy accidents), so it seemed natural to have them translate kidspeak into English.

In the clip, Stamos gets sassy with Fallon, lamenting that of all the show's crazy games (including getting pushed into a phone booth and playing puppy trivia with puppies) he gets stuck with "a dud." But it's the fact that Stamos doesn't like the game that makes it so much fun to watch.

Sources: The Tonight Show Starring Jimmy Fallon