Ryan and Sandra's Change-Up Premiere and More!

Sandra Bullock (in Lanvin) caused quite a stir when she made a surprise appearance at the Hollywood premiere of pal Ryan Reynolds' new flick, The Change-Up. "I don't [have a date] tonight," Reynolds was quick to tell the curious reporters on the red carpet. "Unless my brother counts." Click through the gallery to see Olivia Wilde, Beyonce and more stars at last night's hottest parties!