HE'S THE BLOND ONE. THE CUTE ONE. THE ONE WITH ONLY SLIGHTLY More Facial Stubble Than That Sixth Sense Kid. But Nick Carter, 20, the youngest of the five milky-voiced Backstreet Boys, has been retooling his sweet towheaded looks of late. For one thing, there's the trio of freshly inked tattoos. The shark on his left arm "is a reflection of my personality," says Carter. "A shark can be very quiet; it can be very dangerous, it can be very sleek." Adorning his right arm is a Native American-style chain. "I wanted something tribal," he says. On his right shoulder is a musical note "because I'm a singer." Carter's other new alteration: the shearing of his golden locks, which he had worn longer and often parted down the center since age 10. "It was tiem to change," he says,"but I didn't know if people would be like, 'Oh, I don't like him anymore because he doesn't have that long hair!'" He needn't have worried. if anything, Carter's more mature look only enhances his appeal, says L.A. stylist Rachel Zoe Rosenzweig, who works with the Boys. "He's growing into himself," she observes, "and he's just getting sexier." Carter says that the group's rigorous performances keep his 6'2" frame in dancing form. And although he's on the road about 200 days a year, he often returns to the Tamp area, where he was raised by his parents, Jane,41, who oversees 12-year-old brother Aaron's singing career, and Robert, 47, a retired truck driver. Carter, who earned a GED because his work kept him from high school, shares his waterfront Florida hom with a 19-year-old music-biz girlfriend he won't name--- partly to protect her from Jealous fans. "The screams for him are endless," says Carson Daly, host of MTV's Total Request Live, where the Backstreet Boys and their videos bring out lovestruck legions. "His fans are very possessive." The fervor suits Carter just fine. "What guy couldn't say that he likes women being after him?" he asks. "I'm not going to lie. It's Great!" Just call him the One Who's Having the Most Fun.