By Sara Vilkomerson
Updated November 26, 2014 at 04:00 PM EST
Larry Busacca/Getty Images

Unbroken, directed by Angelina Jolie, tells the true story of Louie Zamperini (Jack O’Connell)—who, among other things, survived 47 days adrift on a raft after his plane went down over the Pacific along with Russell Allen ‘Phil’ Phillips (Domhnall Gleeson) and Francis ‘Mac’ McNamara (Finn Wittrock). The actors went on an extreme diet for the two months before filming began, and found themselves with plenty to bond over once shooting got underway. “The three of them were so hungry,” says Jolie. “Every time I’d go and sit near them they were always talking about food.”

Gleeson says that they’d try to make each other laugh: “We also spent a lot of time talking about food and what we’d eventually eat.” So when Gleeson’s day to go off his diet arrived, O’Connell decided to help him celebrate. “I took off all my clothes and waited in his trailer for him, naked with a pizza box,” he says. “When he came in I opened the box and said, ‘Do you want more cheese with that sir?’ He just cracked up.” O’Connell laughs. “I knew he was having to deal with the sight of my balls and everything else being very close to his food.”

For more on Unbroken, pick up the latest issue of Entertainment Weekly on stands now.