A more fully developed work than Chuckle, Weiss' satisfactory latest--but with an ending that, like Chuckle's, is a mite pat. At age one, Hank acquires a stuffed hippopotamus and says ""Oogie!,"" which becomes the hippo's name. At age two, with a firm ""Hank and Oogie,' he rejects a teddy bear. At age three, he insists--in response to his father's reservations--""Oogie is beautiful."" At four, he takes Oogie to nursery school. At five, entering kindergarten, he reluctantly lets his mother take Oogie home: two boys have snorted, ""Big kids don't play with dolls."" (His consoling ""You'll learn to get along without me"" to Oogie at lunch--the very words his mother has said to him--is a high point of the book.) But he must still have Oogie with him at meals, at bathtime, and in bed--until Oogie, washed, takes so long to dry that Hank must do without him. . . even at bedtime. The next morning he sets Oogie on the shelf next to his other toys, content to look at him before falling asleep. In story terms, the resolution is psychologically unmotivated (in contrast with the first, school-time parting)--though, in real life, accidents do join with readiness to bring results. A partial problem here is the too-close programming, hence the seeming contrivance. But if the story has little resonance--except, occasionally, in the spare, shades-of-Goffstein pictures--it could still ease youngsters into a relinquishment like Hank's.