THE BOYS' BRIGADE

Remember actor Zac Effron showing off his butt in a nude underwear on a movie set? Well the actor who's shooting 'Dirty Grandpa' was supposed to ride a motorcycle butt naked but he became camera shy and declined.

Butt double

He said he wouldn't do it. He said "my butt isn't for your viewing pleasure".
So they brought in a butt-double to step in for him.

So when you see the movie and you see that scene, know it isn't Zac's butt.