THE FIRST SHOW that Benji Compston, Ash Cooper, and Jonny Allan played was a resounding success—with a certain age bracket.

"We played this one show in like east of London, in Essex, and it was one of our first—I think it might actually have been our first gig," says Compston. "We played a couple of songs to a crowd that I think was expecting a really quite heavy band. And we cleared the room, apart from these two toddlers who ended up slow dancing in front of the stage."

The trio hadn't picked a band name at that point, but Happyness is the word that appears on their terrific debut album, Weird Little Birthday. (Perhaps fittingly, the cover features a toddler grimacing for the camera.)

"We all grew up in London, and came together through various musical circumstances, like playing in each other's bands and knowing each other's friends through growing up in the same neighborhood. Being into the same kind of music, that kind of thing," Compston says. "We just started writing and demoing and recording and hanging out in our rehearsal studio in South London, and that's basically how the album came together. We just took our time, hanging out and playing songs."

Those songs belie the group's casual approach, an element that the press has been quick to dub "slacker rock" and compare to any number of indie-rock bands from the '90s: Pavement, Dinosaur Jr., Wilco, Sparklehorse, Grandaddy. But Happyness' imprint is distinct and impressive, with a firm basis in musicianship (the band members frequently swap instruments as it suits the song), adroit and self-aware songwriting, and indelible chemistry between the three members. "Pumpkin Noir" is a sleepy-eyed ramble with nihilistic underpinnings, while "Leave the Party" is a potential anthem delivered in an appealingly low-key, late-night manner. And "Great Minds Think Alike, All Brains Taste the Same" is a two-minute pop blast with oohing falsetto harmonies and irresistible accusations like "You're cheesy like you don't know" and "You ate my birthday cake!"

The writing and recording process was impulsive and relaxed, says Compston. "Where we recorded the album was an old kind of dilapidated carpentry workshop in the countryside that has probably now fallen down into a collapsed heap of wood. There were a lot of instruments hanging about and we'd just pick things up and play around with them. If someone else was playing something, someone else would just sit down at the nearest chair and play whatever was there."

Weird Little Birthday—the US edition includes a handful of bonus tracks, including the hilarious "Montreal Rock Band Somewhere"—is an outstanding, confident statement of purpose from an assured young band, encapsulating excitement and boredom in equal measures. Parts of it punch while other parts shrug, although it's likely the latter portion that has led many to term the band "slacker rock."

"It's so funny. We had no idea we were a slacker rock band until someone told us," says Compston. "It's like, oh, okay, we're a college slacker rock band! That's fine, whatever. But we didn't really know that term massively well until it was thrust upon us."

Those easy references points are perhaps unavoidable for a band that's good enough to capture so many ears their first time at bat. Right now, Happyness is focused on exploring America on their first US tour. "We want to go to the McDonald's in Austin where Daniel Johnston handed out his mixtapes," Compston says. "And I want to go to the town outside of Seattle where Twin Peaks was filmed and just kind of sit there and look at that waterfall."