When an email lands in your inbox asking if you want to play Boston Calling, it’s sensible to at least take a minute to think the decision through. But when saying “Yes” means that you get to share the bill with Tenacious D, you accept the invitation right away.

“If we could join Tenacious D onstage and sing backup—we know the songs!—and be involved, we would love to do that,” says Krill frontman Jonah Furman. “Seeing the Pixies is like seeing Stonehenge, but seeing Tenacious D is like seeing Foamhenge.”

Indie rock trio Krill have long been one of our favorite local acts. That said, while their being given the opening spot at this coming weekend’s Boston Calling is undoubtedly deserved, the news was a bit surprising. “It’s funny seeing emails [listing] the bands at Boston Calling like Beck, Tenacious D, the Pixies … and then Krill,” says drummer Ian Becker. “It seems like a joke.”

Openers are typically poppy or cheerful. Krill’s no bummer band or anything, but their songs, many of which are riddled with anxiety, sarcasm, and overarching metaphors, do tend to travel along weirder routes. “I envision the people throwing things at us,” jokes Furman. “Isn’t that what happened to Pavement at Lollapalooza in the early days?” says guitarist Aaron Ratoff, referring to the infamous incident where rocks thrown onstage caused Scott Kannberg to moon the crowd. “People hated it on that tour, which is weird to think about because … it’s Pavement. Maybe ‘weird’ music like theirs would be more accepted than the crazier bands on that tour.”

It’s natural that Krill has been thinking about this stuff. Boston Calling will be their largest crowd to date; up until now, the Hopscotch Festival in Raleigh and a one-off show at Bowery Ballroom in Manhattan have been their biggest shows, clocking in an average of 550 people staring back at them. “In terms of high stages, we played a tall one in Richmond that used to be a fire station,” Becker laughs. “That was for like 40 people and we must have been 10 feet in the air.”

They’re not as nervous as expected. In fact, they sound pretty calm. “There’s a lot of factors that make a show pleasant to play or not scary, and I think only one of those things is the amount of people,” says Becker. For Krill, the size of the crowd doesn’t alter the deliverables. “People need to stand in a good formation, though,” adds Furman, who admits he gets nervous playing to large crowds sometimes. “That’s important, filling the space like an elevator.”

The push to go poppy for a festival is pretty much nonexistent for Krill. They change minor sections in their songs on tour, but that’s for their own stability. “I wonder if anyone really notices it as much as we do,” says Ratoff. “We’ll draw out weirder parts in the songs and try to improvise slightly.” He continues: “We’re not Phish or anything, but there are minor jams … It’s the last show of the tour, so there may be some of that.”

Becker suggests playing “Shipping Up To Boston” mid-set. Furman one-ups him, and jokes about bringing a youth orchestra onstage. “At this point, it’s hopeless,” he says. They may be joking, but those kind of unpredictable moves tend to work in these environments.

“In general, festivals have grown to become weirdly cartoonish events.” says Becker. “You’re seeing a band, but there’s noise bleeding in from another set happening or the crowd is so large that you can’t see the stage. Plus so much is prioritized over the actual performance at festivals; there’s all these tents and people are wasted in the middle of the day. It’s a sea of people, you can’t see anything, and it’s expensive. Some festivals aren’t like that, and Boston Calling seems to have solved a lot of those problems.”

Plus, in this case, Tenacious D will be there. When Krill first says they’re dying to play with the duo, I think they’re kidding. But they aren’t. “That’s my number one want, more than the Pixies, more than Beck,” says Ratoff. “Run the Jewels are cool, but Tenacious D are far and away it. We need to play with the D.”

As star struck as they’d be next to the D, Krill explain that their admiration isn’t necessarily for Jack Black or Kyle Gass as individual celebrities, but rather for the comic duo as a whole.

“We would love to meet them,” Ratoff says. “We would love to engage with them in any way. I want to see them perform. That would be enough.” He pauses for a breath and then sums it up: “It’s a big deal for us.”

BOSTON CALLING W/ KRILL. FRI-SUN 5.22-24. CITY HALL PLAZA, 1 CITY HALL SQ., BOSTON. 12PM/$75+. BOSTONCALLING.COM