Ryan Reynolds had to buff up to fit into his skin-tight Green Lantern suit.
The Proposal star, who plays the eponymous superhero, endured hours of training for elaborate fight scenes and joked about eating little more than "wood chippings".
"I had to wear that suit, so I put in my required time in the gym," he said.
Ryan, who made his comic book adaptation debut as Deadpool in X-Men Origins: Wolverine, also had to overcome his fear of flying through the air to film scenes, where the Green Lantern ring gives him the power to swoop through space.
"I was initiated early. On the third day, they basically fired me 200 feet into the air at 60 feet per second and that got me over it right quick, without an adult diaper or anything," he said.
"After a while, you're playing on these wires, they're so articulate - and I was getting quite cocky by the end. I loved it - the best way to get over the fear is just to do it."
The 34-year-old heart-throb confessed the role harked back to his childhood days.
"I'd never worked on a movie that required this much imagination. It really felt like being a kid again. Everything you're seeing in this world I have to imagine and express through my eyes for the audience, and that was a big challenge," he said.
:: Green Lantern is in cinemas now.