"They're both slightly possessed."

That's Eric Bana speaking on two of his co-stars in "Deliver Us from Evil": Joel McHale and Olivia Munn. The two comedic actors were an unorthodox choice by director Scott Derrickson for the horror film, but kept things fun on the sidelines during the very scary exorcism story.

The Aussie actor was also an interesting choice for the movie, as it is the first horror film on his résumé. "I want the full effect. I wanna be scared, that's what we try to deliver here," Bana told HitFix during our interview. "The full ride... I'd like to do more."

To prep as the lead as New York detective Ralph Sarchie, Bana was given access to tapings of real-life exorcisms. Whether or not he got to watch all that he wanted: "I saw enough. One in particular really freaked me out," he said. "They're not all that fun to watch."

Still, they "educated" the actor; he pointed out that exorcisms while be little practiced in the United States, "there's nothing at all unusual about the subject matter in Africa" and in other cultures. 

Watch the rest of the video above to hear more about the business of getting into character and working with Derrickson. "Deliver Us From Evil" hits theaters Wednesday (July 2).