District 9 won the top spot at the box office in its opening weekend, as the alien thriller drew more than $37 million, which topped second- and third- place finishers G.I. Joe: The Rise of Cobra ($22.5 million) and The Time Traveler's Wife ($19.2 million).

The film's surprise success, according to Deadline Hollywood Daily, can be attributed to a smart, grassroots marketing campaign -- consisting of bus benches warning the seats are for humans only -- from director Neill Blomkamp and producer Peter Jackson.

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• District 9
• GI Joe Rise of the Cobra
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• The Time Travelers Wife