It seems like a season of 'Game of Thrones' is simply not complete without the presence of actual musicians making a cameo in at least one episode. The infamous 'Red Wedding' featured Coldplay drummer Will Champion as one of the band members during the bloody feast, and Mastodon portrayed wildlings in the equally bloody 'Hardhome' from Season Five.

So it shouldn't be a surprise if another band has been spotted on the set of 'Game of Thrones' in Girona, Spain.

According to Watchers on the Wall, members of the Icelandic group Of Monsters and Men have been seen at the Sant Pere de Galligants monastery. Singers Nanna Bryndís Hilmarsdóttir and Ragnar "Raggi" Þórhallsson as well as drummer Arnar Rósenkranz Hilmarsson were identified despite the fact that they were in costume.

Although the roles of the musicians have not been confirmed, their costumes suggest that the Of Monsters and Men band members will be part of the theater troupe Arya Stark will be joining in Season Six.

An appearance from Of Mouse and Men in 'Game of Thrones' wouldn't be a shock, since Nanna Bryndís Hilmarsdóttir had previously confirmed with Interview magazine that the band is a huge fan of the show.

"Yeah, oh my god, we love it," Hilmarsdóttir said. "We're all obsessed with 'Game of Thrones.'"

Nanna Hilmarsdóttir also explained the difference between their first and second album, an explanation that sounded a lot like the band's favorite show.

"It's funny because our first album is very much creature-y maybe, fantasy, but then the album we're doing right now is quite the opposite," she said. "It's very personal; it's human. But in Iceland, it's definitely a lot of stories-I grew up on ghost stories a lot, so I'm obsessed with all that kind of stuff. It's definitely where we come from."

Watch out for Of Monsters and Men in the sixth season of 'Game of Thrones,' which will air on HBO next spring.