Horror hit The Devil Inside had millions of movie goers shaking in fear when it topped the U.S. box office earlier this year, but RadarOnline.com has exclusively learned that one of the film’s stars is far less frightening in real life than on the big screen.

Guests at the 220 Fitness 1st Year Anniversary Party in Santa Monica, Calif., were surprised on Thursday to spot the woman of many a nightmare, Maria Rossi - the mother who killed three church members during her own exorcism, according to the scary tale - in the flesh and blood.

"Wow, this is scary, this place is packed. I thought I was the scary one!" joked Suzan Crowley, the British actress who played Rossi on the big screen, when she joined the crowds celebrating the success of the state of the art gym.

The Devil Inside came out of nowhere and is a monster blockbuster at the box office, knocking Tom Cruise and his big-budget Mission: Impossible out of first place.

The Devil Inside took in a record-setting $34.5 million this weekend. It cost Paramount only $1 million to acquire the horror flick.

Mission: Impossible - Ghost Protocol, which had been atop the leader board for the last two weekends, fell to second place with a still-respectable $20.5 million in ticket sales.

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The Devil Inside movie is following a long line of horror films that have used unconventional methods to drum up publicity, but a screening in a church reached new heights by terrifying movie goers in Pasadena, Calif.

The Devil Inside is about a woman whose mother brutally murdered three people, and is committed to an insane asylum in Italy. Her daughter travels to visit her and convinces two young exorcists to cure her mother, but they meet with four powerful demons.

Audience members had intense reactions to the film. “That was insane,” and “I’m freaked out now,” were the responses of the shocked people.