There are lots of stories about children outgrowing imaginary companions; this gains only passing interest by telling it from the viewpoint of the companion, here a little green beast whose problem is that every child he settles in with eventually goes on to school. And "" 'Once they went off to school,' he would say with a sigh, 'nothing was ever the same again.' "" This begins with his moving in with Marcia, sneaking into her bed to surprise her when she enters the room. Though momentarily alarmed, she accepts this strange bedfellow with undramatic equanimity (no ""Frog Prince"" undercurrents here), and the two are then close companions until she announces she is starting to school. ""He knew just what was going to happen next. Marcia would get busier and busier, and he would get lonelier, and lonelier. It always ends up this way, he thought bitterly, with me getting dumped."" And so he goes off in the rain in search of another child. . . and finds one in Ken. Dillon's idea is a bit cute to start with, and her flat, uneventful story becomes more disappointing as it more or less trails off. Conover's pictures, some of them silhouettes, project a sweet, nostalgic view of childhood but no energy or narrative action.