Paul McCartney didn't recognise Nirvana.
The Beatles legend got together with remaining members of the grunge group to record the tune Cut Me Some Slack a few years ago.
Despite being familiar with Dave Grohl, Paul didn't recognize bassist Krist Novoselic and live guitarist Pat Smear initially.
The singers won the award for Best Rock Song at last night's Grammy Awards.
"Tell you the truth, I didn't know who they were. Seriously. I knew who Dave was 'cause I've met him. But then he said, 'I've got a couple of friends coming along.' And then during the session, I hear them talking, and they're [saying], 'Wow, we haven't played together since Nirvana,'" Paul recalled backstage at the prestigious awards show, reports New York Daily News.
Their collaboration won widespread popularity after the quartet sang it on Saturday Night Live in 2012.
Much to Paul's disbelief, the iconic singer found himself in the middle of a reunion of one of the most celebrated bands of the '90s.
"I found myself in the middle of a Nirvana reunion. And I was very happy. It was magic for me playing with these guys," he enthused.
"They really are great to play with, because they're a great band. They were a great band with Kurt [Cobain, Nirvana's lead singer who died aged 27 in 1994]. And I say, that's what I experienced on the day, just playing with a really good band. Which is a great privilege, a very special thing, and I should know."
Dave echoed Paul's sentiments, and confessed he'd introduced his daughters to music by The Beatles to give them a strong foundation in classic rock.
"There aren't too many things that last forever. And I honestly think that what Paul and the band did will last forever," Dave gushed.
Paul also took to the stage at last night's awards with his former Beatles bandmate Ringo Starr for a long awaited reunion.