For obvious reasons, we’re never getting a Nirvana reunion. But more than 20 years later, the band’s commercial breakthrough remains such a defining moment in pop culture that it’s always newsworthy whenever the remaining creative principals behind ‘Nevermind’ get together — even if we aren’t exactly sure how or why it’s happening.

The latest example is a somewhat mysterious in-studio reunion between ex-Nirvana members Dave Grohl and Krist Novoselic, with ‘Nevermind’ producer Butch Vig manning the controls. Vig broke the news via Twitter, telling followers, “The last 24 hours have been surreal! Had a great gig at the El Rey last night, and spent today recording with Dave, Krist and special guest!”

The sessions mark only the second time the trio has convened since the Nirvana days (that we’re aware of, anyway). The last time they got together, the result was the track ‘I Should Have Known,’ on the Foo Fighters‘ ‘Wasting Light’ album; this time, no one’s saying what exactly Grohl, Novoselic, and Vig are up to.

For Vig, the reunion comes during a busy time — he’s getting ready to release the first Garbage album in seven years (‘Not Your Kind of People,’ due May 15). Meanwhile, Novoselic has stayed busy since Nirvana’s breakup by dabbling in politics (including a brief run for the clerk’s office in Washington’s Wahkiakum County) while contributing to a number of musical projects, including Foo Fighters and Flipper.

Grohl has reportedly been working on a documentary about Sound City Studios, where ‘Nevermind’ was recorded, prompting speculation that the session could have been assembled for the film. As for who the special guest might be, we can only speculate. What are you hoping to hear from the reunion?