'Kung Fu Panda' drops to second place.

'The Incredible Hulk' roared into first place in the weekend box office with an estimated $54.5 million, studio estimates showed. 

The $150 million action flick, a collaboration between Marvel Studios and Universal Pictures, stars EDWARD NORTON as scientist Bruce Banner, who desperately hunts for a cure to gamma radiation that poisons his cells and transforms him into a rage-filled muscular green monster.  

The DreamWorks animated comedy 'Kung Fu Panda' finished in second place, earning an estimated $34.3 million its second weekend, a drop of 43 percent. The family-oriented feature utilizes the voices of JACK BLACK, ANGELINA JOLIE and DUSTIN HOFFMAN, as it tells the story of a panda named Po who pursues his dream of becoming a Kung Fu master.

M. NIGHT SHYAMALAN's 'The Happening' came in third place with and estimated $30.5 million for the weekend. The $60 million thriller stars MARK WAHLBERG as a teacher who takes his family on the run to escape a natural crisis presenting a large-scale threat to humanity. 

ADAM SANDLER's 'You Don't Mess with the Zohan' finished in fourth with an estimated $16.4 million. The Columbia Pictures (Sony) movie stars Sandler as Zohan, an Israeli commando who fakes his own death to pursue his dream of becoming a hairstylist in New York City. 

In the fifth slot was 'Indiana Jones and the Kingdom of the Crystal Skull,' the latest installment in the HARRISON FORD blockbuster series, which took in an estimated $13.5 million.