-Zac Efron celebrated his 21st birthday with friends on Saturday night. Starting off at Pace nightclub, fellow partygoers included Zac’s co-star girlfriend, Vanessa Hudgens, along with pals Monique Coleman, Ashley Tisdale, Jared Murillo, Brittany Snow, Amanda Bynes, Aly and AJ Michalka and Michelle Trachtenberg. Pics below. (Credit: GossipGirls)