The Inception star plays killer whale trainer Stephanie in the upcoming drama, but during one of her routines, which is set to the 2010 pop track, Cotillard's character loses her legs when a stunt goes wrong.
And because the movie scene was so traumatic, the 37 year old admits just the thought of Perry's track sends her into a dark place.
She tells New York Magazine, "I think it's a good choice for such a horrific event. It's very expressive... I'm not a big Katy Perry fan, but the song had a big impact on me. Now when I hear it, I feel uncomfortable. It makes me, not exactly sad, but it's hard for me to listen to. I tense up, and I feel very emotional."