The British star couldn't face seeing a passionate kiss between her and co-star Logan Lerman and found it difficult to shoot her sexy portrayal of Susan Sarandon in a Rocky Horror Picture Show tribute scene.
In the scene, the brunette beauty is almost unrecognisable in a revealing corset and lashings of lipstick, and she insists the role was a world away from her studious Harry Potter character, Hermione.
Watson tells BBC Radio 1, "It's really funny because when I watch the film back, there are a few things I can't watch. I can't watch the Rocky Horror dancing scene, and I can't watch the kissing scenes.
"This film really pushed me out of my comfort zone. I told the director (Stephen Chbosky) that I have just come from playing Hermione Granger and you are expecting me to dance and putting me in corsets, and it's difficult."