Prime primate entertainment: Mrs. Mundis shows that raising a chimp in a New York apartment involves more than 15 pounds of bananas a week. It means reluctant sisters, shredded Pampers, and a cage bolted to the dining room wall. Boris, a little ""fluff ball,"" came from a pet store and stayed for more than a year while the Mundis family doted and coped. They nursed him through pneumonia, taught him to walk on grass, and endured his phases--water play, swinging, spitting, nudism--natural in the wild but not in the living room. He nibbled their son's arm regularly, played can't-catch-me with the dog, and scared a wino neighbor already in D.T.'s. At a party he worked the crowd for champagne and goodies, then surprised the guests with ice cubes in their coat pockets. Their ""soft wild innocent"" had to move on when Mrs. Mundis became pregnant. Now living in a Chester, England zoo Boris has the best of both worlds (good care, few restraints) and an even larger audience. No, they wouldn't do it again--they had to thwart his natural impulses; here you can share the sentiment and hairy humor without sacrificing a roomful of furniture.