You can always rely on Stephen Colbert to fearlessly grill his guests on the tough issues. And Monday night on The Colbert Report, he hit Iggy Pop with a question that's stymied the rock world for decades: Why doesn't the leather-skinned singer ever wear a shirt when performing?

"The Pharaoh never wore a shirt," the Stooges frontman scoffed. "Geronimo never wore a shirt." Well, this finally settles that question. If the ancient Egyptian monarchs or Apache warriors didn't do it, Iggy won't either. Although I'm not so sure Geronimo ever smeared peanut butter on his body....

As a consolation prize, Pop did give Colbert a more direct answer when asked what musical influence made him want to start the band that basically created punk. "There was a guy named Link Wray and I heard this music in the student union at a university. It was called 'Rumble' and it sounded bad," Pop said nostalgically. "I left school emotionally at the moment I heard 'Rumble.'"

Watch Iggy's Colbert interview above n' check out the Stooges' performance of their Ready to Die track "Job" below. And if you're not familiar with "Rumble" (although you probably do know it from Pulp Fiction), give the garage rock classic a spin. What are you afraid of?