WRITE IN N.Y. By JOSLYN YANG  Email  Archives  Print  Reprint November 1, 2003 -- It seems there's nothing 4-year-old Olivia can't do. That cosmopolitan cutie paints, plays soccer and piano - and when she's not at school, is most likely filling in at a circus. In her latest adventure, "Olivia . . . and the Missing Toy," the energetic piglet - who diapers Edwin, the family cat, and takes him for walks in a stroller - tracks down a stuffed bear with the single-mindedness of Sherlock Holmes. Or Ian Falconer. After all, he's the artist who created Olivia. At 44, he still remembers the toys he loved when he was a boy in Connecticut. "I had a stuffed tiger I used to dress up," the soft-spoken artist tells The Post. "I also dressed up the dog in baby clothes and diapers - then put him in the stroller." At his Manhattan apartment the other day - which has a lush garden out back, and lots of his cartoons for The New Yorker magazine on the walls - Falconer spoke about Olivia's latest saga and the real Olivia: his niece. About seven years ago, he says, he started working on a Christmas present for her - a book about a precocious, energetic 4-year-old who happened to be a pig. Why a pig? "Pigs are just sort of human and they are known to be very intelligent," Falconer says. "Sometimes little kids look like little pigs, with little turned-up noses." Eventually, the present became a book - and the book, a best seller. "Olivia" came out in 2000, followed by "Olivia Saves the Circus," "Olivia's Opposites," "Olivia Counts," "Presenting Olivia" and now "Olivia . . . and the Missing Toy." All the drawings are in black, white and red - though the latest one contains a little green, too, "for variety," Falconer says. Hilary Knight, who drew the Eloise books, is one of the picturesque piglet's fans. "Eloise has met her match," Knight wrote. "We love Olivia!" So do kids. At a book signing this summer, Falconer says, a little girl surprised him by coming up to him holding the first "Olivia" book, the one with his picture on the back. "She's looking at me and the picture. Then she asked me, 'Was this picture taken a long time ago?' " he recalls, with a laugh. "Kids can be very direct!" Falconer's own childhood sounds like a storybook. When he was 10, his architect father and artist mother moved the family to an island half a mile off the Connecticut shore. Ian and his two sisters were ferried to school each day in a fiberglass boat. "It was very pretty, very isolating and had lots of wildlife," Falconer recalls. "We had a skunk, a pet squirrel and a pet seagull." He found the seagull at a nesting ground near his house - the bird had been abandoned there as a baby. Young Ian took the bird home, fed him and named him Henry. "I had him about a year," Falconer says. "He would sit on my head sometimes." Later he returned the bird to the wild, where it belonged. There are no live animals in his West Village town home, but there are plenty of pigs - stuffed ones, bronze ones and pen-and-ink ones. "Pigs get very big," Falconer explains. "It's a little too big to have one in an apartment in New York City." And the real Olivia? She's 10 years old now - and something of a celebrity at her school in Connecticut. "Sometimes kids bring the book [in] and have her sign it," says her artist uncle. "I think she's very proud of it." Who wouldn't be?