Hollywood actor Matt Damon says George Clooney, his co-star and director on "The Monuments Men," fooled him into thinking he was gaining weight. Asked at a recent press conference if the notorious prankster pulled one over on him during their latest collaboration, Damon was quick to share an anecdote. "I read somewhere that he took in my wardrobe an eighth of an inch every other day. He had the wardrobe department do that because he knew I was trying to lose weight," Damon told the reporters about how he finally figured out what was going on. "This was a job where I would go back [from Berlin] to New York where I was living with my family and then I'd come back for two weeks and go back to New York and every time I came back [to Berlin] my pants would be too tight and I was like: 'This is weird. I've been going to the gym.' So, it's nice having friends like that." Based on Robert M. Edsel's non-fiction book "The Monuments Men: Allied Heroes, Nazi Thieves and the Greatest Treasure Hunt in History," the film opens nationwide Friday. It stars Damon, Clooney, John Goodman, Bill Murray and Bob Balaban as members of an over-aged platoon of museum workers, artists and architects who try to protect treasured art works from the Nazis in World War II Germany. The movie was directed by Clooney from a script he penned with his longtime producing partner Grant Heslov. Sitting alongside Damon at the press conference, Clooney joked about hiring him for "Monuments Men" only after Brad Pitt turned down the part. "Casting was fun. We couldn't get Brad, so we got Matt," Clooney quipped. "We hadn't thought of Bob yet and we went to an 'Argo' party and we saw Bob. We had this part and we knew we wanted Bill in it and we kept thinking, 'Who can we put opposite Bill that he can give a really hard time to?' And then we were at this party with Bob and I looked over and I was like, 'It's perfect.' And Grant was like, 'It's perfect.' And so we called Bob up the next day, but the rest of the gang we wrote it with them in mind." Clooney and Damon previously collaborated on the "Ocean's Eleven" trilogy, as well as the films "Syriana" and "The Informant!"