Tom Hiddleston asked Chris Hemsworth to punch him in the face.
The 38-year-old actor struggled to master his fight scenes in 2012 movie 'The Avengers' so urged his co-star - who played his character Loki's on-screen brother Thor - to just take direct action, only for him to go "down like a stone".
Speaking on 'The Late Show', he laughed: "I mean, fighting Chris Hemsworth, you're going to lose. Let's face it.
"On film, it's all about angle when you're fighting. So you're trying to get the angles of the different parts of the choreography to tell the story...
"Thor had to strike Loki across the face and I was wearing the horns, which weigh about 30 pounds.
"I couldn't really sell the hit, the smack. So I just said to Chris, 'I think you should just hit me in the face.'
"I went down like a stone."
Tom was only thankful that the pair were making a movie together rather than starring in a play.
He added: "And I supposed, on stage, when you're doing a fight, you have to do it every night 100 odd performances. I think if I was being hit in the face by Chris Hemsworth day after day, I don't know if I would be able to manage that. It wouldn't be sustainable."
Tom will reprise his role as Loki in an upcoming Disney+ show but is staying tight-lipped on the details.
He simply said: "I can tell you this. In the years since 'Avengers: Infinity War' and 'Avengers: Endgame', which came out this spring, two questions I've been asked: 'Is Loki really dead?' and 'What is Loki doing with that cube?' It's always the cube somehow. And this series will answer both of those questions."