The 'Monuments Men' actor-and-director pranked his co-star by secretly having the wardrobe department take in his clothes every week and Bill admits the entire set were in on the joke.
He said: "The only one who got victimised was Matt Damon. He got Damon pretty good with his uniform. Taking his pants in a quarter-in every week...
"The rest of us just got to enjoy that because we all knew and we'd see him in just firing those abs, really firing them to try and keep those trousers up.
"You'd go 'That's great, do you want to do another set?' and you could see him go like, 'Oh my muscles are fatigued, I'm good', that was good."
Despite falling victim to the prank, Matt insists he had a great time working on the film - which follows an Allied group who try and save pieces of art and other items of cultural importance before their destruction by Adolf Hitler - because everyone was so professional.
He told 'Entertainment Tonight': "It's not that we were like yucking it up or toasting marshmallows on the set or anything, it was really because we've all made a lot of movies and everybody independently appreciated being on a movie where the script was so good, the director knew what he was doing and was in control and where we had fellow cast members who were experienced enough to know that's as good as it gets and it was a best experience for all of us in that way."
And another star of the film, John Goodman says it was one of the best movie-making experiences he has ever had.
He said: "It was probably the most fun I've ever had working on a film. There was a lot of good down time. Swapping lives, telling stories. George was so professional, he had his work done ahead of time."