Zac Efron was so nervous about performing the waltz in the new High School Musical movie -- he put in extra practice with his girlfriend and co-star Vanessa Hudgens.

"I started rehearsals two weeks later than everybody else so I had to put in extra time to catch up," Efron said. "I had to learn the waltz and some ballroom stuff, which was interesting.

"I do not know why people ever did it. It is so unbelievably hard. I thought 'Was this really classed as fun?' It was so difficult to learn. When I got the hang of it and got it down it was OK.

"Luckily with Vanessa, she is so easy to dance with. She kind of leads me. She made it a lot easier but we practiced a lot."

High School Musical 3: Senior Year is scheduled for a theatrical release in the United States on October 24.

Thanks showbizspy.com