George Clooney is famous for his on-set pranks, and although he was busy starring in and directing the upcoming “The Monuments Men,” he still found time to mess with one costar in the movie, Matt Damon . “I read somewhere that he would take in my wardrobe ⅛ of an inch every other day because he knew I was trying to lose weight,” Damon said at a press conference, seated alongside Clooney and costars John Goodman , Bill Murray , Cate Blanchett , Bob Balaban , and producer Grant Heslov . Damon said he would return to New York periodically during filming to spend time with his family. “Every time I came back, the pants were tighter, and it was weird.” Clooney responded with a laugh, “Yeah, just looking out for you.” He noted there wasn’t a lot of time for fooling around during the making of the film, which is based on a true story about a group of men — including art historians and museum directors with Boston and Cambridge ties — who went behind enemy lines during WWII to rescue great artworks being looted by the Nazis. Damon, who had worked with Clooney previously in smaller roles, had nothing but praise for his director. “Honest to God, it was one of the best experiences I’ve ever had.” “The Monuments Men” opens Feb. 7.