Considering the source, take this news with a grain of salt.

In fact, considering the batty circumstances, take this news with an entire mine’s worth of rocksalt, but it’s a rumour too insane not to take notice of… especially if it somehow turns out to be true.

According to UK rag The SunSir Paul McCartney is set to replace Kurt Cobain as the frontman of Nirvana for a special reunion gig for tomorrow night’s star-filled charity benefit concert in New York for the victims of Hurricane Sandy.

The 12.12.12 show is already tipped to be the largest charity show in recent memory, featuring cameos from some of music’s biggest A-listers, including The Rolling Stones, The Who, the recently Australian bound Bruce Springsteen and the E Street Band, and the legendary 70-year-old Beatle.

The speculation surfaces that Macca will be playing with Foo Fighters frontman Dave Grohl, and former Nirvana bassist Krist Novoselic – performing one hand-picked Nirvana classic – for the charity show to help raise money for the Robin Hood Relief Fund.

What song is anyone’s guess, McCartney slurring his knees-up Liverpudlian acccent all over ‘Smells Like Teen Spirit’, or lending his civil croon to a rendition of ‘Heart Shaped Box’?

It’s difficult to imagine, but apparently the surviving members of the grunge band were already secretly rehearsing with McCartney, as well as long-time guitarist and on/off Nirvana and fellow Foo, Pat Smear, in a recent studio session.

According to The Sun, Sir Paul said he rang Grohl, inviting him to come “jam with some mates.” McCartney responded by suggesting they “just make something up” and ended up playing with the drummer, Novosleic and Smear in an unnamed rehearsal space.

“I didn’t really know who they were. They are saying how good it is to be back together,” McCartney allegedly says. “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.”

The story does seem a little far-fetched, but considering Grohl’s connections and McCartney’s willingness to rub shoulders with the younger elite, it doesn’t seem inconceivable that they’d jam together.[do action=”pullquote”]”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.” – Paul McCartney[/do]

After all they’ve done it several times before, with the pair teaming up multiple times since 2009 across multiple performances of Beatles classics and Wings’ ‘Band On The Run’ (google into a world of red herrings at your own peril), most recently and notably, in a four-way jam at the Grammys earlier this year featuring Grohl, McCartney, Springsteen and Joe Walsh trading licks over a Beatles medley.

Still, to take the next step and have Grohl and Novoselic risk tarnishing the Nirvana legacy with a little help from their friends? To an audience of potentially billions around the world? Seems doubtful. Somebody should tweet Courtney Love and get to the bottom of this… or at least get an amazing quote.

All will be revealed when the 12.12.12 Benefit concert takes place tomorrow night at New York’s Madison Square Garden, broadcast live and simultaneously across 37 US TV networks and on the internet, beamed around the world via

The all-star line-up will feature the beloved ex-Beatle, Dave Grohl (possibly together – probably not), along with the likes of hip hop superstar Kanye West, endearing Pearl Jam frontman Eddie Vedder, guitar god Eric Clapton, Pink Floyd bassist Roger Waters, the blue-eyed Chris Martin of Coldplay, as well as performances from The Rolling Stones, The Who, and Bruce Springsteen and the E Street Band.