The U.S. weekend box office is seeing some changes this week. No. 4 goes to the newly released comedy "The Change-Up," which beats the superhero flick, Captain America: The First Avenger's 13 million US dollars with 13.5 million U.S. dollars. Starred by Ryan Reynolds, and Jason Bateman, the film tells the story about a married father who accidentally had his body switched with his best friend, leading to a series of wildly complex situations. The comedy had a good opening weekend, and hopefully it will last in the following weeks. Cowboys & Aliens secured the third position on the list, earning 15.7 million US dollars.And surprisingly, The Smurfs performed a lot better than many people expected. The animated 3D film of the Belgian cartoon character came in at No.2, raking in 21 million US dollars during its second weekend in theaters. The "Rise of the Planet of the Apes" swung in with a chest-beating debut over its first weekend.The conquering Apes climbed to the top with 54.8 million US dollars on nearly 5,400 screens at more than 3,600 locations, ranking as the fourth highest-grossing August opening film ever.