CHICAGO — A gathering of Deadheads and Juggalos: How does that work?

It happened Wednesday night at an Irving Park pub when some Deadheads were surprised to find their regularly scheduled Grateful Dead cover band Terrapin Flyer had taken the night off — and an Insane Clown Posse-inspired duo was playing instead.

"The crowd here last night was definitely not the Terrapin Flyer crowd," said Elisa Yousett, 22, who does marketing for Abbey Pub, referring to the Dead cover band. "The crossover was very interesting."

Fans of horrorcore duo Twiztid, like those of collaborator Insane Clown Posse, dress in white clown face paint and dark clothing and are known as Juggalos.

The late Jerry Garcia of the Grateful Dead (l.) and Violent J of horrorcore duo Insane Clown Posse. View Full Caption Flickr/Zoomabooma and GettyImages/Michel Boutefeu

Juggalos don't shy away from themes of murder and violence, particularly with knives. Deadheads are, well, a bit more peaceful.

About 300 Juggalos filled the venue at 3420 W. Grace St. Wednesday night.

There was "a lot of face paint a lot of dyed hair, a lot of baggy clothes on the guys and very little clothes on the girls," Yousett said. "There was one with white-out contact lenses."

But some fans stuck it out.

Twiztid fan Jason Johnson said he spotted about 10 "confused and afraid" Deadheads, or jam fans who love the Grateful Dead and are known for a signature style of their own: dreads and tie-dye.

Terrapin Flyer plays at Abbey Pub every Wednesday night, and some fans weren't aware they'd taken a rare night off.

Two or three of the Deadheads stayed for the show, but most left when the doors opened for Twiztid, Johnson said.

Doug Hagman, rhythm guitar player and singer for Terrapin Flyer, said he posted on the band's website and Facebook page that they wouldn't be playing, but a show posting still circulated on some concert sites.

"I think most people got the message," Hagman said. But, "I heard some people saying, like, 'What the heck happened?' The guy at the door told them, [and] they just kind of laughed. It wasn’t a big problem."

Terrapin apologized for any confusion on its Facebook page the next day:

"[W]e apologize if you showed up to see us last night and were surrounded by Juggalos," the post said.

Patrons waiting for a comedy show on the restaurant side of Abbey Pub also were surprised to see the Juggalos, some of whom stopped to watch the stand-up.

The comedians took notice.

"There were a few comedians who were very educated on the Juggalo culture, which were fun and funny. ...The comedians had a lot of stuff to work with. I don’t think they knew ahead of time what they were getting in to," Yousett said, adding that the comedians riffed on Faygo, a soft drink popular in Juggalo circles.

"A lot of Juggalos liked the comedy show," Yousett said.

But some Juggalos didn't appreciate the humor at their expense, said comedian Samuel Priest.

A female comedian was "aggressively clown heckled" after taking some shots, and a "particularly angry Juggalo" acted as though he was going to approach the stage.

"It got a little heated in that moment...but overall it was fun/weird," Priest said.

Another Twiztid fan, who preferred not to be named, said the night was largely peaceful.

"Some of them seemed a little taken back by us...[but] everyone seemed to be having a great time to me, all in all," she said.

Terrapin Flyer will resume its regularly scheduled tribute night next week. Doors open at 9:30 p.m., and tickets are $7.