Kristen Stewart
K-Stew is by no means known for her cheeriness, but that's only because she's the kind of celebrity who doesn't seem to love being in the spotlight. During her time in the Twilight franchise, Stewart earned a reputation for being cold and unapproachable, which was only worsened after she was caught cheating on Robert Pattinson with the married director of Snow White and the Huntsman. Fortunately, Stewart has since matured, and seems to be doing quite well for herself!