Heaps of makeup transformed the all-star cast of "Cloud Atlas," which premiered at the Toronto International Film Festival, "startling" the cast members themselves, they said.
Actor Jim Broadbent quipped that he loved working with Hugh (Grant), but that he did not know it was him until he swore in his thick English accent.
Grant, who celebrated a birthday on Sunday, said "plastic was applied to their faces for hours" each day during filming.
"I heard only one complaint and that was out of (actor Jim) Sturges... (over a) sticky beard that had grown on his face over the course of the film, at the end of the day he said, 'Please take this thing off my face,'" Tom Hanks said dryly.
Actor Hugo Weaving said the cast members, which also included Halle Berry, Doona Bae, Keith David, Susan Sarandon, David Gyasi, James D'Arcy, Zhou Xun and Ben Whishaw, transcended race and gender in multiple roles and were "unrecognizable" in the thick makeup.
"There was that sense of nervous excitement about going into the next day (of shooting), the next character," he said.
Sarandon as a man in the film, said: "When I looked in the mirror I couldn't even see myself, which was really the first time that's ever happened.
"Despite all the various things I've done to myself in film, I've never looked in the mirror and thought, 'Is that Chris Walken's cousin?' That was a startling experience not recognizing myself at all," she said.
Berry said she most enjoyed playing a "white German Jewish woman" in the movie.
"I was having a fitting and I remember Tom (Hanks) said to me while I was trying on all of these beautiful dresses trying to figure out what looked best on her and Tom said, 'Have you ever done a period piece before?' and I said (hesitant), 'Yeah.'
"And he asked, 'Have you ever worn clothes like this (in these films)?' and I said, 'Tom, think about it for a minute... For me to have played in that time period I was probably a slave or close to it, and not dressed up as formally.'
"It was one of those heavy moments but we found a way to laugh about it and I thought, 'Great, that's why I get to do this, to play something that I would never get to play in life, I would never get to dress up like that and be that character if I was really me,' so that was very poignant for me as an artist to get to do that."
Directors Tom Tykwer ("Run Lola Run") and Andy and Lana Wachowski ("The Matrix") created out of David Mitchell's landmark novel a globe-spanning, time-tripping, gender-hopping epic film.
Its strings connect a nineteenth century notary (Sturgess) who keeps a journal of his voyage across the Pacific, a musician (Whishaw) in 1931 writing to a lover, a journalist (Berry) investigating a murder at a nuclear plant in California, a publisher (Broadbent)'s pursuit of gangsters in present-day Britain, a robotic clone (Bae) interviewed on the eve of her execution for rebelling against a totalitarian regime that created her in a dystopian future Korea, and a tribesman (Hanks) in a post-apocalyptic Hawaii who is visited by one of the last survivors of a dead civilization (Berry), just to name a few.
At its core, Hanks said the film is an "example of cinematic literature that examines the connections of the human race throughout all of time."
The story's characters "had to make a choice between cruelty and kindness and that decision was going to change the world from hereon in," he explained.
Being a part of the film, despite the makeup headaches, Hanks (who has never before appeared in a science fiction movie) concluded "was totally worth it if only to see Hugh Grant as a cannibal."