With its whistle solo and bongos, infectious melody and cute boy-girl vocals, Peter Bjorn and John's "Young Folks" is an irrepressible joy. Like the best novelty songs or one-hit wonders, "Young Folks" worms itself into the brain immediately; resistance is futile, even thought there's something cloying about its sugary hooks.

After its release this year on PB&J's third album, Writer's Block, the song spread from the band's native Sweden to the indie-rock blog world to the TV show Grey's Anatomy, and it brought a sold-out crowd to the TLA - sorry, the Fillmore at the TLA - on Thursday night.

As on Writer's Block, guitarist Peter Morén, bassist Björn Yttling and drummer John Eriksson jumped around, musically and physically, from sad-sack ballads to bashing guitar rave-ups to new-wave pop.

Shorn of keyboards and other textures that brighten the album versions, "Poor Cow," "Amsterdam" and "Paris 2004" fell flat. Morén, who took the lion's share of the vocals, possesses a nasal voice better suited to propulsive tunes like the Krautrocking "The Chills," the zippy, mod "It Beats Me Every Time," the throbbing "Up Against the Wall" and the closing medley of the Concretes' "Teen Love" and the Undertones' "Teenage Kicks."

For "Young Folks," PB&J brought out Heather D'Angelo from Au Revoir Simone (an all-female synth-pop trio from Brooklyn whose opening set was charming but static, as all-keyboard groups tend to be) and a bongo player. Morén's whistling was bolstered by a recorded backing track. The song sounded like a novelty, even in the band's own set: hook-filled, multidimensional, perky. And folks young and old bounced and danced.

Fujiya & Miyagi, the third trio on the bill and the second with a geographically displaced moniker (they're British blokes) also got the crowd moving with Stereolab-like percolations and spiky guitar riffs.