Fans of heavy metal and HBO's "Game of Thrones" can rejoice knowing that the episode that aired on Sunday night on HBO featured a rare occurrence for the show, according to Stereogum.

This powerhouse drama on the premium cable network has reveled in its most authentic use of the fictional universe, mostly vowing to make sure that they keep all references to real pop-culture out of the show.

That basically means that cameos by well-known people in Hollywood or other pop-like sensations have been largely left out of the show. Series creator Dan Weiss, though, has been known to throw a few in there, just for the sake of it. But their appearances are largely masked and mostly presented as an extra to the scene.

In the scene with the "Red Wedding," Coldplay drummer Will Champion helped play the musical number "The Rains of Castemere."

Also, during Joffrey's royal wedding, members of Sigur Ros played the court musicians.

But it's last night's episode that really got fans stirring on Twitter. That's because it featured members of heavy metal band Mastodon playing wildling warriors north of the Wall. That includes Brann Dailor, Bill Kelliher and Brent Hinds.

It can also be surmised that it did not take much to dress Mastodon up as the wildlings, given the fact that they already closely resemble them.

They were invited to the show by Weiss, who is also a big fan of their music. They also contributed a song, "White Walker," to the show's "Catch the Throne Vol. 2" album recording earlier this year.

Dailor issued a statement on the appearance.

"It was such an incredible experience to be on set as extras for our collective favorite show 'Game Of Thrones' and to be wildlings murdered and then brought back to life by White Walkers was beyond amazing," Dailor's statement read. "I watched my best friends Brent and Bill, murdered right in front of me as I myself was stabbed in the stomach and had my throat slit multiple times, and I didn't mind at all. It made me love being in Mastodon even more. We are more than privileged and honored to have been a part of one of the greatest stories ever told on film, and the catering wasn't bad either."