Tonight's (Dec. 12) 12-12-12 concert is already the most star-studded music event of the year -- and, given that all proceeds are going to Hurricane Sandy relief, also one of the most altruistic. Now, according to reports, it'll also play host to a truly unforgettable rock reunion.

It's worth noting up front that this information comes from the UK tabloid the Sun, whose habit of running stories based on anonymous (or just plain nonexistent) sources tends to produce some fairly colorful gossip. So with that out of the way, here's the (alleged) scoop: Paul McCartney will play frontman for the surviving members of Nirvana during the show.

The story goes that McCartney recently played with Dave Grohl, Krist Novoselic, and Pat Smear during a secret studio session that started when Grohl called the former Beatle to see if he'd be interested in stopping by to "jam with some mates." McCartney's quoted as saying, "I didn’t really know who they were. They are saying how good it is to be back together. I said 'Whoa, you guys haven’t played together for all that time?' And somebody whispered to me 'That’s Nirvana. You’re Kurt.' I couldn’t believe it."

We're taking this with a huge grain of salt, obviously, but if we've learned anything about Dave Grohl over the years, it's that almost anything is possible where he's concerned -- and if he feels like raising some money for hurricane relief by assembling an unlikely-seeming all-star jam, he'll do it. According to the report, the group will not tackle a Nirvana classic, but rather perform a new song for the event.

Either way, you'll be able to watch the whole show even if you aren't in attendance at Madison Square Garden tonight -- it'll be streaming on this YouTube page, which is currently displaying a helpful countdown clock to help you pass the minutes before 12-12-12's impressive lineup takes the stage.

Watch the '12-12-12' Concert Streaming Here