If you believe the Imagineers who work for British tabloid The Sun, tonight's 12.12.12 benefit concert will be memorable for several reasons ... including the part where Paul McCartney plays Kurt Cobain in a Nirvana tribute.

Yes, in what's sure to be the most memorable onstage reunion since Dr. Dre and Snoop performed alongside Hologram Tupac at Coachella — provided it's actually true — McCartney will join former Nirvana mates Dave Grohl, Krist Novoselic and Pat Smear at Madison Square Garden tonight, where they'll "play a new song" written during an impromptu jam session.

"I didn't really know who they were," The Sun quotes McCartney as saying. "And somebody whispered to me 'That's Nirvana. You're Kurt.' I couldn't believe it."

Of course, it bears mention that none of this may actually be true (reps for McCartney would only tell MTV News they could "neither confirm nor deny" the Sun story), but the idea of a septuagenarian rocking out with the surviving members of Nirvana certainly has us thinking ... so here's some hypothetical highlights from what's sure to be a show-stopper, in more ways than one.

» McCartney and Nirvana do "Smells Like Teen Spirit": Paul prefaces the song by telling the MSG crowd "In my day, 'Teen Spirit' smelled like Camphor and penny candies!" Everyone responds with polite applause.

» Dave Grohl dresses up as Ringo: Insists on working "Yellow Submarine" into the set, bums everybody out. Though his drum solo on "The End" is markedly better than the original.

» McCartney tries his hand at "Negative Creep": Has to get oxygen midway through the first verse.

» Paul spends half the set explaining the history of flannel: Did you know it was produced in carding mills in towns like Hay on Wye?

» New Nirvana hires Steve Albini to do sound: He takes 16 hours to get the mics just right, still ends up burying McCartney's vocals in the mix anyway. Is replaced midway through the set by Scott Litt.

» Grohl ceremoniously crosses another accomplishment off his 'Rock Dreams' list: He keeps it folded up in his back pocket just for occasions like this. For the record, at this point, the only things remaining are "Jam with Cyborg John Bonham," "Climb Mt. Kilimanjaro with Rob Halford," "Get warts like Lemmy."

» Set highlights include: An incendiary version of "Drain You," a transcendent "Something in the Way," an apoplectic rant from Courtney Love, who was eating at the Sbarro across from MSG when she found out about this whole thing.

» The "new song" actually ends up being a cover of "Band on the Run": Which is fitting, considering the Foo Fighters are basically just the Wings of Nirvana, only with balls.

Are you looking forward to McCartney and Nirvana? Let us know in the comments below.

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