FUSE TV - Behind the Scenes at 12-12-12 Rehearsals: Paul McCartney, Billy Joel & The Who

12-12-12 kicks off tonight at Madison Square Garden—catch it at YouTube.com/Fuse at 7:30p/6:30c—and rehearsals for the Hurricane Sandy relief concert are already underway.

While Paul McCartney, Billy Joel and The Who were tuning up last night, Fuse was lucky enough to witness these legends during their soundchecks. And even though these were only rehearsals, we can promise you the atmosphere in Madison Square Garden is already electric.

Paul McCartney's Soundcheck

As befitting a knight and a Beatle, McCartney took the stage first. Sir Paul may be way past 64 at this point, but close your eyes while he's rocking and you'd be hard pressed to notice it. McCartney's soundcheck was almost a mini-concert: He joked around with his crew, brought some awesomely special guests onstage (you'll have to watch it to find out more!) and even lit up the pyrotechnics during his practice run.

While we can't tell you exactly what McCartney played, we might be able to let it slip that he played two songs from a certain self-titled Beatles album. He even delved deep into his catalog, delivering a non-single Wings track (it's an underappreciated gem). Also, we would be remiss to mention he had not one but TWO lava lamps onstage.

Billy Joel Soundcheck

Billy Joel—who we spied playing air guitar during McCartney's set—rehearsed his material next. Joel's between-song banter was just as jubilant as McCartney's... and a lot stranger. He tested his mic using a semi-obscure quote from Dumb and Dumber. No, we're not kidding. In case you're wondering, he imitated Jim Carrey handing out tips saying, "There ya go, there ya go." For further entertainment, he jovially made fun of his emerging second chin.

Most memorably, Joel treated everyone to an impromptu send-up of "We Are the World" that almost certainly won't make the main 12-12-12 concert. Here's a sampling of his rewritten lyrics: "We are New York, we are New Jersey: We got f--ked by the hurricane so please start giving." Don't expect to hear that on the TV broadcast.

The Who's Soundcheck

Late into the night, the Who delivered an abbreviated version of their 12-12-12 set. And while we're not going to tell you what they played, we can guarantee it was high-octane as hell. Pete Townshend's arm did 11 full windmills during the first song alone.

Check back for more behind-the-scenes coverage of the 12-12-12 rehearsals. And don't forget to donate to the victims of Hurricane Sandy—many people are still reeling from the devastation. Live stream the 12-12-12 benefit concert tonight at 7:30p/6:30c on Fuse's YouTube channel and Fuse.tv or watch the live broadcast on our cable network. The concert will be available for purchase on iTunes afterwards, with the proceeds going to charity.