The 46-year-old Oscar-winning actress said she was unsure if they would be able to successfully pull it off, reported Contactmusic.
"It was very ambitious. Something I had never read before. It was a challenge to do something unique that would test everybody in new ways. I thought, 'Wow, if they can pull this off and do it all independently, and get to really have their vision...," she said.
The film, which also stars Hugh Grant, Jim Broadbent and Susan Sarandon, uses heavy prosthetics to tell the story of several inter-connected characters throughout time.
Although the shoot was tough, Berry's co-star Tom Hanks said the mood on set was far from glum.
"From the get-go we knew it was going to be very big. That the engineering was going to be tough. That the logistics were going to be very hard. They seemed so happy to see us every morning. It wasn't like, here comes Mr Wacky-head, who's going to shout out his jokes. It was, 'You're here! We get to have more fun!," he said.
