Justin Bieber and Selena Gomez had a chance to party with Katy Perry & Robert Pattinson. The whole gang attended a party after Katy’s premiere of Katy Perry: Part of Me. Selena is a known friend of Katy’s and Justin was her very obvious date. Rob is a good friend of Katy’s as well, along with Kristen Stewart (who could not attend). The gang had a chance to hang out and party together after the big event. As for how Selena and Justin got in, we’re not sure since both are still under 21. Unless they were invited in for a private party that had no drinks. You can see a video all about their night out on the town down below this post.