56 minutes in the movie, we see Reed Luplau's firm bubble butt.
One minute later, Ryan Steele is naked too.
We see both their butts for a couple of minutes as they are making love on the floor. We see Reed Luplau's bush but no full frontal nudity.

Twenty minutes through the movie, Heath Ledger is getting out of the shower. As he is drying himself up, we get a good view through the mirror at his dick and butt. He has a nice uncut dick with bushy pubic hair. Mid movie there is a quick scene in a bathroom, Bruce Greenwood is seen naked entering a bathroom stall. During that quick scene, we can clearly see his butt.

6 minutes in the movie, Robert Webb is biking naked. We get a good look at his uncut dick. He is in a nudist camp so we get to see a bunch of other people naked.
17 minutes in the movie, Robert Webb is naked again.
78 minutes in the movie, he is naked again as he is getting married.

Will Young, openly gay, is briefly seen completely naked around 40 minutes in the movie. We see his big ass, and although he is sideways, we can clearly see he has a very large and long uncut dick. We will hopefully get to see more of naked Will Young soon.

Tyler Nilson appears completely naked and features frontal nudity. We see his cut dick and butt first in close-up as he stands next to John C. Reilly. We know it's not a stunt as we see him again from further away later in the scene. We see later John C. Reilly naked but it's obvious that the butt shots are stunt. A nice butt but we don't know who to give the credits to!

In this movie, Zachary Booth and Emile Hirsch have small roles. When Emile gets on stage, Zachary is dancing naked in the background. Then Emile also gets naked. We get views of both of them dancing naked with their dicks dangling around.