callhim Joe Winchell wasn’t always a monster. As a sophomore at Pierson High School, he discovered his passion for the stage when he agreed to take a small role in a friend’s play. “I actually didn’t say anything,” Winchell recalled. “But I remember having a lot of fun.” He has since gone on to study theater in college, and perform in numerous local productions, most recently signing on to play King Duncan in a rendition of “Macbeth” being staged this summer as part of the Long Island Shakespeare Festival. Yet this week marks a major turn in the young actor’s career. Now, in movie theaters across the country, Winchell is making his big screen debut. As “Jellyfish Guy.” Yes, that’s Winchell beneath the large, translucent fish head and iridescent body suit standing behind Will Smith’s character in “Men In Black III.” (You can catch him lumbering over James Edwards about 15 minutes into the film.) Winchell, a Sag Harbor native, simply answered an open casting call in New York City at the urging of a fellow acting friend in the summer of 2010. And — as luck would have it — he walked away with a part. “They were looking for tall people,” Winchell explained, very matter-of-factly. At 6’2” with a wiry build, it turns out Winchell had the perfect proportions for an intergalactic jellyfish. To prepare for the role, Winchell had to take a cast of his face, which he said wasn’t too terrible (even though he had to sit still for a good 15 minutes and breathe through a straw while the plaster hardened). The biggest challenge came on set. The mask itself was heavy, made up of two pieces that came together at the bridge of his nose — “I couldn’t really see, but I could hear,” Winchell explained — and the costume was made of two different jumpsuits: a tight-fitting bottom layer covered by a loose-fitting plastic layer. “It was awkward as hell,” Winchell said. And hot. “There were all these white lights beaming down on us, and when I would get too hot, the suit would start fogging up,” he added, only somewhat sheepishly. “In between every take they had to fan me down.” But, while sweating profusely and visually impaired, Winchell said he was thrilled to be surrounded by well-trained professionals — that made it all worthwhile. He took mental notes on their techniques. Tommie Lee Jones performed vocal exercises before scenes; Will Smith did push-ups in between takes. But, he noted, Smith also spent time talking about the dynamics of his character and the evolution of the aliens with director Barry Sonnenfeld. “I loved the fact that he was taking the time to make this good,” Winchell added. “One of the last things I heard him say before we were finished shooting was, ‘This ain’t easy. If it were easy, everyone could do it.’” For Winchell, standing there on set in a jellyfish head, the statement seemed to resonate.