It's a rare occurrence when a documentary winds up as the No. 1 film at the box office, but that's what is likely to occur this Labor Day weekend with the debut of Morgan Spurlock's (Supersize Me) 3D documentary One Direction: This Is Us. Tracking studies indicate that the Sony/TriStar movie, which features interviews and performances of the English boy band (one of the members is Irish) during their recent world tour, will collect $18-22 million at the box office, largely from teenage girls, who ordinarily would be making plans to return to school after this weekend. (In 2008, Hannah Montana/Miley Cyrus: Best of Both Worlds Concert Tour opened in first place over Super Bowl weekend with $31.1 million; two years ago the Justin Bieber concert documentary Never Say Never opened in second place on the weekend before Valentine's Day with $29.5 million.) But while the One Direction gang -- Harry Styles, Niall Horan, Louis Tomlinson, Zayn Malik and Liam Payne -- are expected to clean up this weekend, another teen/tween icon, Selena Gomez may find things as Rocky as her tabloid-friendly relationship with Justin Bieber. The former Disney Channel star's new action film Getaway, in which she costars with Ethan Hawke, has received not a single positive review from a major critic and is likely to earn no more than $4-6 million, according to forecasters. A third new film, Closed Circuit, starring Eric Bana, is opening in only 870 theaters. Forecasters say it will take in around $3 million.