Drawing rhythm from “The House That Jack Built,” and part of the plot from Gingerbread Boy, Willard (The Moon & Riddles Diner and the Sunnyside Café, 2001, etc.) sends a surprise birthday party hilariously awry. Just as everyone’s ready to sing, out leaps the mouse from beneath Grandma’s bonnet, followed by the cat, and in the confusion, her huge birthday cake topples. But it springs to the door and rolls away, with the partygoers in hot pursuit. In her strong, stylish debut, Mattheson supplies soft-focus scenes in warm browns and luminous purples that add both a feeling of intimacy and sidesplitting details, including a wonderfully insouciant cake that is last seen sailing gaily downhill ahead of its would-be devourers. “The cake’s run away! Things couldn’t be worse!” wails the young narrator, but she might be about to change her mind at the end: “I hear a bee in Grandmother’s purse.” Rib-tickling reading, at party time, or any time. (Picture book. 6-8)