Paul McCartney was in the Grammy Awards, jamming with the survivors of Nirvana. However, according to a conspiracy theory/urban legend, the real Paul is jamming with Kurt Cobain in the afterlife.

So who was on the stage with Dave Grohl on Grammy night? According to the "Paul is dead" theory, it is an impostor. From the Beatles Bible entry titled 'Paul is dead':"McCartney was said to have been replaced by a lookalike, called variously William Shears Campbell or William Sheppard. William Campbell allegedly became Billy Shears on Sgt Pepper."

Why is there an impostor? Because, as the claim states.."Paul Is Dead." On the assumption that Paul McCartney did die, why would they need an impostor to make people believe otherwise? The rationale was stated in TruTv.com: "Because of all the money the Beatles contributed to England's tax coffers, their continued success was vital to the financial health of the nation."

While that reason is highly speculative, it did lead to some more burning questions: How and when did Paul allegedly die? From TruTv.com:

"Piecing together clues from songs, films and album covers, conspiracy buffs have come up with this scenario: During the early-morning hours of November 9, 1966, Paul argued with his bandmates in the studio while recording songs for their Sgt. Pepper's Lonely Hearts Club Band album. He left in a huff just before 5 a.m. While driving to a friend's house, Paul picked up a female hitchhiker who couldn't control her excitement when she realized who was behind the wheel. She lunged to hug Paul, causing him to lose control of his Aston Martin. It smashed into a stone fence and burst into flames, killing them both. Paul was decapitated and burnt to a crisp, making a positive ID difficult. Despite no evidence to support either the story of the fatal crash or of a cover-up, the rumors persisted."

Part of the reason why those rumors persisted (until now, apparently) was that there were, as proponents of the theory claim, "clues" from the Beatles' subsequent work. They were referred and quoted by the advocates of the rumors. The original paper trail from Beatles Bible:

"The first known print reference was in an article written by Tim Harper which appeared in the 17 September edition of the Times-Delphic, the newspaper of the Drake University in Des Moines, Iowa.

Harper later claimed that he wasn't the original source for any of the claims in his articles. He said he got the information from a fellow student, Dartanyan Brown. Mr Brown is said to have got the story from a musician who had heard it on the Californian west coast, and that he also read the story in an underground newspaper. "

Another related incident that added fuel to the fire. Beatles Bible recounts: "..on 12 October 1969, after an on-air phone call to radio presenter Russ Gibb, a DJ on WKNR-FM in Michigan. The caller, identified only as 'Tom', claimed that McCartney was dead, and instructed Gibb to play Revolution 9 backwards, where the repeated "number nine" phrase was heard as "turn me on, dead man".

Other additional clues, from TruTv.com: "In the "Magical Mystery Tour" film, as the group performs "I Am the Walrus," Paul in stocking feet stands next to an empty pair of blood-spattered shoes and the drumhead reads "Love the 3 Beatles" (implying, perhaps, that there were only three surviving members of the group)."

"'Let It Be' was the second-to-last Beatles album to be recorded, but the last to be released. On the cover, Paul is the only Beatle whose face is partially obscured (by a microphone). He is also the only one not photographed in profile and with a white background. Paul's background is blood red."

"On the cover of the last album that the Beatles recorded, "Abbey Road" the band is photographed crossing Abbey Road in London, outside of British music company EMI's Abbey Road Recording Studios. Paul is out of step with the other Beatles, barefoot and with his eyes closed. In many countries, including England, bodies are buried shoeless. Also, the way that the Beatles are dressed on the cover is said to have this meaning:
       Lennon in white - the preacher
       Starr in black - the undertaker
       "McCartney" in a suit and barefoot - the corpse
       Harrison in blue jeans and work shirt - the grave digger"

The Beatles themselves seems to be amused by the rumor. None of them ever admitted that the "clues" mentioned were in reference to Paul's death. Even if they were, there is still the possibility that it might be done in jest. McCartney had already reacted with a slice of humor as recounted by Beatles Bible: "In an edition of Life magazine dated 7 November 1969, McCartney reassured fans that "Rumours of my death have been greatly exaggerated," paraphrasing Mark Twain. "However," he continued, "if I was dead, I'm sure I'd be the last to know." The cover of the magazine featured Paul with eventual wife, Linda. The caption read: "Paul Is Still With Us." 

It is possible that the Beatles played along with the rumor. If that were true, then the Beatles were not only the greatest rock band, they were also masters of 'trolling.'