Anna Kendrick and Casey Affleck were ''competitive'' when voicing 'ParaNorman'.
The pair lent their talents to an animated film for the first time in the movie and while they found it easier navigating the dialogue together, the two stars went out of their way to ''embarrass themselves''.
Anna said: ''I got to record my first day with Casey Affleck. He'd never done it before either. We were both really new to it and it was a great way to start out. By the end of the day, we were getting more and more comfortable, and it became a little competitive to see who was willing to embarrass themselves more. Who won? Probably Casey.''
Anna - who voiced cheerleader Courtney Babcock in the 3D stop-motion animated adventure movie - was happy that she and Casey were encouraged to use improvisation when they recorded their scenes.
She said: ''That was the other great thing about having Casey there, because I have a crush on him in the film. We got to do a lot of stuff and the directors were so open to improv because, according to them, the process is so slow and so precise that those moments of spontaneity are so important. Anything you can do to keep that process spontaneous helps them later.''