Help, Mama, Help!

``If it ain't broke, don't fix it,'' goes the popular maxim-a caveat that these collaborators have wisely heeded with their latest saga of Baby Chick and Mother Hen. The fowl stars of Hatch, Egg, Hatch! and Chicken Pox! again lend charm and whimsy to even the simplest situations-as, in this case, when a ghost invades Baby Chick's backyard tent. And again the interactive devices prove funny and clever; particularly sweet is the pull-tab that causes the scared chick to leap into his mama's waiting wings. Little fingers can pat the soft tummy of ``a big, furry mouse,'' and when a doting Mother Hen tucks her young'un into his sleeping bag, kids can assist by pulling up a real zipper. Baby Chick may need some help, but Roddie and Cony have their formula down pat. Ages 3-5. (Apr.)