Fluff and Billy

In Killen's (Not Me!) sophomore picture book, it's all fun and games until someone gets nailed in the chest with a snowball. Although the eponymous penguins could just as easily be friends as relatives, it's hard not to see their relationship as that of older and younger siblings, with smaller Billy, distinguished by a splash of yellow, mimicking Fluff's every action as they cavort on the ice. "%E2%80%98I'm climbing up!' said Fluff. %E2%80%98I'm climbing up!' said Billy. %E2%80%98I'm sliding down!' said Fluff, %E2%80%98I'm sliding down!' said Billy." When an overexcited Billy takes things too far ("%E2%80%98I'm rolling a snowball!' said Fluff. %E2%80%98I'm throwing a snowball!' said Billy"), a rift forms between the two, though it's nothing a few good-intentioned tickles can't solve. Killen's watercolors create a pared-down Antarctic landscape defined by judicious use of pale blue%E2%80%94splotches of paint suggest water droplets and snow, zigzags hint at far-off mountains, and halftone-style dots create shadows beneath Fluff and Billy's webbed feet and bulky bodies. Her beaky penguins are adorably childlike in their interactions, movements, and enthusiasm in this sweetly simple story. Ages 3%E2%80%936. (Sept.)