Katy Perry is set to host SNL tomorrow night, but today she was joined by Matt Damon, Val Kilmer, and Andy Samberg on the streets of NYC to film a skit. Katy kept her new haircut hidden under a brunette wig and put on her best smile for the camera. Katy joked about hosting SNL, saying, "I'm up for a challenge, for something new. I love to be challenged . . . I married Russell Brand." Matt's been the featured star on the late-night show in the past, but this time he's just stopping by for a digital short. He's been busy promoting his upcoming holiday release, We Bought a Zoo, and even stopped by The Late Show this week to chat with David Letterman. Matt's made a habit of doing his best Matthew McConaughey impressions during past visits to the talk show, and this time was no different. Damon lightheartedly channeled the other famous Matt after some coaxing from Dave.