Credit: Kevin Mazur/WireImage

Last night, Katy Perrykicked off the Teen Choice Awards at L.A.'s Universal Amphitheater with her apropos new single, "Teenage Dream." The singer/host was joined at the ceremony by a host of big- and small-screen stars, including Ashley Greene, Robert Pattinson, Megan Fox, Kristen Bell, Taylor Lautner, Leighton Meester and all of the Glee girls including Lea Michele. Most of the ladies, despite their varied looks, stayed true to one style rule: that of the short hemline. But the real scene stealer of the night was surprise attendee Sandra Bullock, who took the stage to perform a rousing dance with Betty White to Lil Jon's "Get Low." For a full run-down of the night's fashion plus award-winner spoilers, click through our gallery now. The show will air tonight, at 8 PM EST, on Fox.

—Rachel Jacoby, with reporting by Andrea Simpson