The 29-year-old plays the feline femme fatale in 'The Dark Knight Rises' and is the first female villain in Christopher Nolan's 'Batman' trilogy.
"I didn't realise I was the first - and I feel a little nauseous. That's a lot of pressure," a website quoted Hathaway as saying.
"I'd always thought I was pretty healthy and I always thought I had worked hard in the gym. It turns out that what I thought was hard, in Catwoman's world is actually light to moderate," she added.