MORE PHOTOS: Check out some up close pics of the incident

But "Life & Style Weekly" has heard from a so-called "insider" that he WAS. Sort of.

Supposedly, the show's producer, MARK BURNETT . . . (--The guy who created "Survivor") . . . cleared the prank with Eminem ahead of time.

HOWEVER . . . Eminem was NOT aware of just how BARE Bruno's buttocks were going to be . . . so that might have bothered him a little.

But one man claims Eminem knew EXACTLY what was coming. A comedy writer by the name of Scott Aukerman . . . who claims he was the head writer for Sunday night's show, revealed as much on his blog.

He said, quote, "They rehearsed it at dress [rehearsal] and yes, it went as far as it did on the live show."

Meanwhile, another "insider" claims that Eminem was Burnett's SECOND choice. His first was PARASITE HILTON. She turned him down.

Did you notice, by the way, that the normally very hairy Sacha Baron Cohen was quite HAIRLESS Sunday night??? We'd heard that Sacha BLEACHED his hair blonde to make it harder to see . . . but if you ask me, he was SHAVEN on Sunday night.

Watch the Clip Again!


Let us know, do you think Eminem was in on it?