Fed up at last after finding his cap in the toilet, Peter plops little Emily into a wagon and tries to peddle her to the neighbors. Fortunately, or unfortunately, depending on one’s point of view, Emily turns out to be a hard sell—“ ‘Say Peter,’ he told her. ‘Poo-pee,’ said Emily, tugging at her diaper”—and by the time he’s been pinched and bitten, had to chase after her, and twice saved her from disaster, she’s back in his good graces. Pedersen (Bravo, Mildred and Ed, not reviewed, etc.) depicts her all-rabbit cast in fine-lined, pale watercolors, capturing both Peter’s irritation and Emily’s innate cuteness to a tee. The plot may not be that new, as readers of Martha Alexander’s Nobody Asked Me If I Wanted a Baby Sister (1971), Morse Hamilton’s Little Sister for Sale (1992), and the like can attest—but rare is the big sib who won’t sympathize with Peter’s impulse, or understand his eventual change of heart. (Picture book. 6-8)