hat leather jacket pants sneakers Greenday rock star Green Day has been a popular alt band since the '90s but they really broke into the mega-big time this century with American Idiot.

That's why we're kind of confused as to why they're choosing to promote their new album, 21st Century Breakdown, with shows all week on Last Call With Carson Daly!?!

I mean, you'd think they'd do the week-long stint on Conan, Dave or at least one of the Jimmy's, but the least watched show that airs at 1:30 am?