'Mortal Instruments' Auditions Made Jamie Campbell Bower A Little Nervous

In just a few weeks, fans of "The Mortal Instruments: City of Bones" will find out if Lily Collins and Jamie Campbell Bower have what it takes to recreate the chemistry of Clary and Jace from the beloved YA book.

The two young actors seemed to have hit it off, but when they first met, as they recalled to MTV News at San Diego Comic-Con, the chemistry was anything but electric.

Read more after the jump!

"For me, going into that room, where [Lily] had already been cast, it's such a big deal going in for a screen test for a major movie," Campbell Bower said. I went on to the lot, and there I am on the lot going for an audition, and I was going, 'Oh god, this is just going to be a disaster.' I didn't feel right for it at all. And then the moment I got there, I felt sort of comfortable around you. I felt really just sort of like we'd known each other for years."

Collins could only agree with Campbell Bower's assessment. "I thought I had known him for years," she said. "Jamie had been someone I, from the get-go when they asked me about casting Jace, had put forward from day one. And before he even walked in the room, in my mind, I was really set on this guy coming in and blowing it away. And I hadn't really met him before, and he came in and that was it. I think I knew before I think I knew."

"The Mortal Instruments: City of Bones" opens on August 21.