Ryan Reynolds "flipped out" after he came face-to-face with a bear on a camping trip as a teenager.
The 42-year-old actor was on a school expedition to Canada's Garibaldi Provincial Park when he and his tentmate were woken to the sound of the creature scratching its back on the side of their tent.
He recalled: "We naturally flipped out. I don't think they make diapers secure enough for teenage boys at that age when something like that happens. My eyes were the size of dinner plates."
The 'Deadpool' star pulled out a jackknife - but not because he planned to tackle the bear.
He said: "It was just so I could cut a hole in the tent so we could go out the other side if we needed to.
"We screamed bloody murder. The bear took off pretty quickly once we screamed."
The following morning, the group's leader, who was an experienced bear tracker, looked at the prints left by the bear and found it was just a cub being a "rascal".
Ryan told the USA Today newspaper: "It was baby bear scratching its back on the tent, and being a rascal.
"I'm sure this cub meant no harm and was probably checking us out. But it's still a sign to get the hell out of there. Because mama is going to be close by."
The 'Green Lantern' actor - who has daughters James, four, and Inez, two, with wife Blake Lively - has had other bear encounters since then after visiting Clayoquot Sound on the west coast of Vancouver Island.
He recalled: "You could see 10 different black bears in a day. But you don't want to get close and interfere with their daily life ... in the same way you don't want them to interfere with your life."
And Ryan has narrated director Ian McAllister's new documentary, 'Great Bear Rainforest', which features grizzlies, black bear and the rare white spirit bear - and it was a "privilege" to work on the project.
He said: "To see the area through that giant IMAX lens is a true privilege."