This being a Morgan Spurlock movie, it’s hard not to wish he’d structured it like Super Size Me, wondering what happens to a person after subsisting for a month exclusively on one insidiously innocuous UK boy band. But Spurlock’s One Direction: This Is Us doesn’t even put on investigative airs, and seems therefore about as journalistically useful as a promoted tweet. In 3D, it documents multiple mild-mannered hangouts with the pop juggernaut cobbled together by Simon Cowell from individual auditions on The X-Factor, and is a testament to puppet-master Cowell’s special (pre sex-scandal) genius: None of these lads seems superfluous to their shared enterprise, even if they all are. On stage in packed arenas, Harry, Liam, Louis, Niall, and Zayn come together electrically, like robot-lions forming Voltron. Offstage, seeming alternately and adorably like regular blokes or a basketful of puppies, they do some reflecting on their good fortune amid much goofing around. Perhaps most illuminating are their amateur mob-psychology experiments, impishly conducting crescendos and decrescendos of girlscream, the basic unit of their cultural currency. Non-fans will think it a Zzz factor, at least until being rendered defenseless by those sweet, sweet boys and their sweet, sweet tunes.