Mysterious posters have popped up in cities around the world, leaving Radiohead fans wondering if they point to an upcoming 20th anniversary celebration of the band’s OK Computer.

It’s unclear who is behind the posters, which have already been seen in London, Berlin, Amsterdam Los Angeles and New York, but they seem to reference lyrics from the album track “Fitter Happier," and bear a resemblance to the concept art of that era. The years 1997-2017 also appear on the posters.

Fans are falling all over themselves on Reddit to generate new theories on what the posters represent and what may be coming. Ideas range from a deluxe anniversary reissue of the of the album with unreleased tracks to full album shows to — and even mention of a new, politically fueled album.

The album, Radiohead's most popular with fans and critics alike, was released on May 21, 1997.

Amid the rumors, Radiohead’s collaborator Stanley Donwood recently teased on Instagram an upcoming project with the band that is “soon to be real,” but has since posted only images of scaffolding.

Radiohead recently concluded a North American tour in support of their most recent album, A Moon Shaped Pool. The trek included a technical difficulties-plagued set at the annual Coachella festival, which according to our editor is what the band gets for skipping Ohio this time around.

Radiohead Albums Ranked in Order of Awesomeness