The Missing Muggs: One familiar mug was missing Tuesday among all the smiling faces on the celebrations marking the "Today" show's 40th anniversary--chimpanzee J. Fred Muggs. A svelte 13 pounds when he made his debut on the show in January, 1953, at age 10 months, Muggs reportedly is now a big, round 175 pounds. "With his size now, I'm not sure it would be practical to have him here in person," an NBC spokeswoman said. However, Muggs' co-owner Buddy Mennella called it "a snub," and complained that J. Fred has never gotten his due. "He helped make that show what it is, and now he's just forgotten," Mennella said. . . . Meanwhile, Japan's latest heartthrob is three feet tall, wears diapers and enjoys chewing his toes. He's Jiro, a 6-year-old monkey who has reached stardom through his antics on TV and stage--including an imitation of President Bush collapsing.