Go Wildcats! 'High School Musical 3: Senior Year' held its official premiere at the University of Southern California, and only ET was first on the red carpet with Zac Efron, Vanessa Hudgens, Ashley Tisdale, Corbin Bleu and the rest of the cast of the hugely anticipated, phenomenal musical series sequel! Watch Zac tell ET about his 21st birthday plans, and see Ashley tell us why she dyed her locks brown!

"I'm sure I'll have fun, but we're not going to go big," Zac tells ET about his upcoming birthday plans. "I'm not going to go to Vegas or anything like that -- I'm going to lay low."

Also, watch Vanessa answer questions about what she has in store for Zac's big day.

'HSM 3' brings more drama, more romance and more catchy musical numbers to viewers when the highly anticipated Disney film hits the big screen on October 24. It's the popular crew's last year of high school, and they find themselves struggling with the reality of being separated from one another once they head to college. So, what better way to address their hopes and fears about their future than to stage an elaborate spring musical?

Watch ET for all the highlights from this incredible 'HSM' event!