Zac Efron celebrated his 21st birthday with an exclusive party on Saturday night.

The "High School Musical 3: Senior Year" star enjoyed the gathering at Los Angeles' Pace restaurant with his "High School Musical" co-stars Ashley Tisdale and Monique Coleman, as well as his girlfriend Vanessa Hudgens and pals including "Hairspray" star Amanda Bynes.

Vanessa Hudgens claims she was attacked last week, not Zac Efron. The "High School Musical" stars - who are enjoying an off-screen romance - were leaving London's Apollo theatre last Wednesday when a man in his 40s pushed past security to approach the pair.

Although it had been reported he lunged for Zac, 20, his 19-year-old girlfriend insists the unnamed man cut her face.

Zac Efron was attacked by a crazed fan in London. The "High School Musical" star was leaving the Apollo Theatre with girlfriend and co-star Vanessa Hudgens on Wednesday night when the middle-aged man lunged at him, prompting his five security guards to intervene.

One onlooker said: "It was pretty scary. No one knew who this guy was or what he might do. You hear of all sorts of attacks on stars."

Zac Efron injured himself while shooting "High School Musical 3: Senior Year." The 20-year-old actor - who plays basketball player Troy Bolton in the Disney franchise - admits he "ate it" while filming a scene where he danced in a revolving hallway.

He said: "We had always talked about doing a scene in a revolving setting and then one day I walked in and there was a revolving hallway. It was like a square inside a big hamster wheel. I got there and the crew said, 'OK, let's go!' I was like, 'I haven't rehearsed yet guys!'"