AUSTIN – Most years at South by Southwest, there are “secret” shows you’ve got to sniff out. Some are more secret than others – everyone knew two years ago Metallica was launching its version of Guitar Hero by playing a gig. But others, like an afternoon performance by the Beastie Boys a few years back, are kept more tightly under wraps.

This year, it wasn’t so much an issue of who, but where and when. Tuesday night was the world premiere of Foo Fighters: Back and Forth, and when a band comes to town to attend a screening, you can be pretty sure they’re playing. As badge holders lined up at the Paramount Theater for the movie, SXSW staff members walked through distributing yellow wristbands with “FF” printed on them, telling everyone to head over to Stubbs after the screening but being cutely hush hush as to why.

It seemed the secret show had found us.

First, the movie. Foo Fighters: Back and Forth tracks the band’s 16-year career, from its formation out of the ashes of Nirvana and Sunny Day Real Estate, to numerous lineup changes, to a king-making gig in front of 85,000 people at London’s Wembley Stadium. As Dave Grohl put it in introducing the film, “This is the movie where we all get fat.”

The walk through the band’s history underscores that Foo Fighters is Grohl’s band, first and foremost. And he’s not always the best people person. Original drummer William Goldsmith learns of his firing basically by hearing the rest of the band is holed up in L.A. rerecording its second album. Grohl’s former Scream bandmate Franz Stahl joins the band, only to be dumped when he doesn’t quite fit in. And current guitarist Chris Shiflett always feels original member Pat Smear’s presence lurking (Probably with good reason since Smear’s now back in the band.).

If Grohl comes off as kind of a dictator, the film also captures he and the rest of the band’s easy humor. Grohl may be the funniest man in rock, and he’s always got a one-liner at the ready. Of course, he also got quite the potty mouth – if others cuss like a sailor, he cusses like an Admiral – so not a lot can be passed along. But one line that scored big with the crowd came as Grohl described his frustration with constantly having his first album compared with Nirvana. “What did you want me to do, make a reggae record?”

The most insightful part of the film comes in the last third, when we see the band recording its upcoming album, Wasting Light. Grohl decided he wanted to get back to basics, so he invites the band, along with producer Butch Vig, to record the album in his California home. The footage offers a glimpse into the artisitic process as well as a couple of real-life moments. As Grohl is working hard to finish recording a guitar part, he gets a persistent tap on the shoulder. It’s one of his little girls, who sweetly reminds him, “You said we were going to go swimming!”

The doc offers a fun ride through history and a backstage pass for Foos fans. It’s scheduled to play in theaters on April 5 and will also run on VH1.

Right as the house lights came up, half the crowd beat a path to the door to get in line at Stubbs. As it turns out, that wasn’t really necessary – anyone with the special yellow wristband easily got into the venue, as well as plenty of others. At 9:15, the band walked out on stage, and Grohl gleefully announced to the crowd, “We’re movie stars!” Then the next 40 minutes or so was a straight ahead, no chit chat, workmanlike plow through of Wasting Light, which offers some trademark Grohl screaming and stacked Foos guitars as well as moments of melodic and structural experimentation.

After that, the question that hung above the crowd was clear: Thanks for playing the new album and all, but is there still time for the hits? It was a legitimate question as Tuesday night was supposed to be headlined by Fitz and the Tantrums, who were bumped to later in the night when the Foos decided to play.

Grohl reminded the crowd of that fact a few times, teasingly informing everyone that the band can’t play all night as it launched into “Times Like These,” Everlong,” and pretty much every other big hit the band has ever had, including a nearly 15 minute reading of “Stacked Actors.” “We hijacked someone else’s gig, so we don’t have all the time in the world,” Grohl said at one point. “Let me quickly introduce you to the band – That’sChris.That’sNate.That’sPat.That’sTaylor.I’mDave.ThisisMyHero.”

Ninety minutes after it started, the show was all over, ending appropriately with the band’s first single, “This is a Call.” For fans who watched the movie followed by the show, the last 16 years had come fill circle.