For Josephine, a piglet with aplomb, growing up doesn't mean giving up her baby blanket--and any child under similar parental pressure will savor her symbolic victory. There is, indeed, less trauma than pertinacity here. Past babyhood, we hear and see, ""She took it with her everywhere. . . and she always found a use for it."" It's a flying cape when she soars on the swing, a knapsack when she goes to the market. In time, from patching and trimming, it looks woebegone--and Daddy gets cross. ""Geraldine covered her ears."" Mama tries to hide it; Geraldine, quickly finding it, pins it to her dress in the daytime and tucks it under her pillow at night. Then, after Mama and Papa talk ""in whispers,"" Aunt Bessie, who gave Geraldine the blanket when she was born, gives her ""a new present"": a doll named Rosa, whom Geraldine loves. No more blanket, as Mama and Papa insist? Not Geraldine: with scissors, the blanket is made over--""Now Rosa has the blanket,"" says she, ""and I have Rosa."" In deft, spare, pink-and-gold-tinged cartoons, it all looks as lovable as the blanket, as spiffy as Geraldine.