Gaurdians of the Galaxy is the third-highest box-office opening of 2014 and set a record for the biggest August opening, following Transformers: Age of Extinction and Captain America: The Winter Solider. Not too bad for a movie about a humanoid tree and a racoon in space.

The 2014 American superhero film is the tenth installment in the Marvel Cinematic Universe and features an ensemble cast including Zoe Saldana, Bradley Cooper, Chris Pratt, Vin Diesel, Djimon Hounsou, John C. Reilly, Glenn Close, Benicio del Toro, Dave Bautista, Lee Pace, Michael Rooker and Karen Gillan. Studio projects and audience surveys estimated an opening of $60 to $75 million.

Guardians of the Galaxy is directed by James Gunn, who co-wrote the script with Nicole Perlman. In the film, the main character, Peter Quill (aka Star-Lord), teams up with some alien rebels who are on the run. The script is taken from a pretty obscure comic book within the Marvel titles and did not seem like a blockbuster contender. Since its opening, though, Gaurdians of the Galaxy is holding water with other big hitters in Marvels‘ lineup like Captain America, Iron Man and Avengers.

Gunn told the Los Angeles Times that he was in shock.

“For the past two years, all I’ve been doing is driving forward, making this movie,” Gunn said. “Now I’m done and I’m standing outside of it, and I’m going, ‘How did you guys let me get away with all that?’”

Luc Besson’s Lucy, starring Scarlett Johansson, came in second at the box office, bringing in $18.3 million in its second week. The James Brown biopic, Get On Up, also opened this weekend, earning an estimated $14 million at the box office and coming in third. Transformers: The Age of Extinction remains the year’s highest grossing film, earning $1 billion at the box office worldwide.