Justin Bieber is the guest host in the Season 9 opener, which finds the teen pop star pranking pals Taylor Swift, Rob Dyrdek, Sean Kingston and Miley Cyrus.

Bam Margera pranks his famous friends, including rapper Tyler, the Creator; "Jersey Shore" star Ronnie Magro; and actor Tyler Posey .

Hayden Panettiere is the guest host. Prank victims include Dianna Agron, Zac Efron and Nicole "Snooki" Polizzi.

Tyler the Creator is the guest host. Prank victims include Shenae Grimes, Scott Disick and The Wanted.

Lucy Hale is the guest host. Prank victims include Ian Harding, Vanessa Hudgens and Josh Hutcherson.

Nick Cannon is the guest host. Prank victims include New Boyz, Ashley Tisdale and Demi Lovato.

Dax Shepard is the guest host. Prank victims include Metta World Peace, Lauren Conrad and Chloe Moretz.

Miley Cyrus is the guest host. Prank victims include Kelly Osbourne, Khloe Kardashian and Liam Hemsworth.

Heather Morris is the guest host. Prank victims include Joe Jonas, Cody Simpson and Emma Roberts.

Kellan Lutz is the guest host. Prank victims include Julianne Hough, Ashley Rickards and Aimee Teegarden.

Ashton Kutcher is the guest host. Prank victims include Kim Kardashian and Drake.

Mac Miller is the guest host. Prank victims include T-Pain, Wiz Khalifa, Darrelle Revis and Neil Patrick Harris.