It looks like Katy went out and joined the silly-Perry military! And what's with the funny 'stache? LOL!
Will Ferrell is known for being a jokester, but when he teams up with Bieber the prankster, all bets are off. Just don't mess with his hair, Will!
Kendall of Big Time Rush just loves to sign silly sentimental symbols to his fans.
RAWR! Victoria Justice shows her claws to the paparazzi. Don't get too close, this woman is wild!
Cameron Diaz goes a little loco over winning a KCA blimp.
Is that Nick Jonas dressed up as a hotdog vendor?! Buy one for us, Tay-Tay!
Miley Cyrus doubles as a master of disguise on Late Night with Jimmy Fallon.
Dylan and Cole go crazy for the cameras at a charity event in California. Silly Sprouses!
Taylor Swift and Katy Perry just love to clown around when they're dressed like disco divas.
Jack Black shows off some of his cuckoo karate moves while promoting his Kung Fu Panda sequel.
Talk about a sugar rush! Jennette McCurdy goes bonkers in the land of lollipops.
Miley Cyrus can't help but flash a silly smile to the cameras on the KCA Orange Carpet.
Say cheese! These SpongeBob pals just can't stop horsing around while posing for a family photo. Squidward is NOT amused.
King Julien is known for being the silliest lemur at the Central Park Zoo. Just look at his maniac moves!
Maybe Train should change their name to "Plane" because it seems like frontman Pat Monahan is dying to take flight!
This is the moment Selena Gomez found out she's ACTUALLY dating the Biebs...Just kidding, but she is going gaga over something!
Ready To Rock
Usher's known as Mr. Smooth, but he still knows how to get a little silly (at least in the name of rock-n-roll).
We know that Emma Watson's got some fashion sense, but pig ears? Are those really in right now?
The Jonas Brothers get super silly for the KCA cameras at the awards in 2006.
iCan't Stop Laughing
From showing their guns to playing a mean air guitar, this silly group knows just how to keep us ROFLing.
Bean Bag Bouncing
Brenda Song plays a high-flying round of musical bean bag chairs with friends, Ashley Tisdale and Devon Werkheiser.
Big Time Jokers
The boys of BTR can never stop clowning around!