Katy, John, Nick and Nina in This Week's Celeb Twit Pictures!

Celebrities had their cameras in hand and ready to capture pics from their exciting travels and adventures this week. Nina Dobrev returned to work on the set of The Vampire Diaries and enjoyed a mid-afternoon snack while Nick Cannon got carried away after a costume party. John Mayer took a self-portrait and Katy Perry celebrated her number one hit from the road — click through to see all the photos!