Peach-hued Gitty is a curly-headed, relentlessly optimistic girl; her -unflappable friend- Kvetch is a grumpy purple bird. They share a Jewish heritage, expressed through a few visual hints (a Star of David and Hebrew rendition of Gitty-s name on her bedroom wall) and through Kvetch-s Yiddish-peppered conversation (his very name is defined in the book-s Yiddish glossary as -to complain on and on and on-). Gitty has made a -perfect painting- for the duo-s -perfect, purple tree house,- and as the two head in its direction, she refuses to see any portent in the dark clouds overhead. Kvetch, however, predicts -more than a shprits- (-Time to move our tuchuses!-). When the rain spoils the painting and Gitty-s mood turns Kvetch-like, the bird takes a turn as the sunny one-even as Gitty-s initial reaction to his cheer is an uncharacteristic eye-rolling -Oy vey.- Debuting author Pritchard-s sweet-natured storytelling makes a strong case for friendship-s resilience-and balancing capabilities-while Landy-s (The Spacesuit) digital cartooning and washlike textures have plenty of bounce and bubble. Ages 4-8. Author-s agent: Ginger Knowlton, Curtis Brown. Illustrator-s agent: James Burns, the Bright Agency. (Aug.)