The 23-year-old 'Harry Potter' star said though she was initially confused but she quickly realised it would be a fun film to do, reported Contactmusic.
"I thought it sounded crazy. I remember trying to get my head around it on the phone to my agent who was like, 'So, it's Seth Rogen and Jonah Hill and James Franco and Danny McBride and all these other comedians. Seth Rogen and Evan Goldberg are making it, and all the actors are playing themselves, and it's going to be the end of the world.And they want you in the movie." she said.
Initially, Watson had so many questions about the storyline of the movie.
"I am like,'What? Why? How? I just remember reading it and thinking it's hilarious, I thought it was the most crazy, absurd premise for a story I'd ever heard. I had to do it.
"I was taken aback. Why did they think of me? But then I read the script, and it was so funny. And I loved that they made the only two women in the story these really strong and funny characters. We come off so well," she added.