The Astounding Broccoli Boy 
 
Rory Rooney likes to be prepared for all eventualities. His favourite book is Don't Be Scared, Be Prepared, and he has memorized every page of it. He could even survive a hippo attack. He knows that just because something is unlikely doesn't mean it won't ever happen . . .
But Rory isn't prepared when he suddenly and inexplicably turns green. Stuck in an isolation ward in a hospital far from home with two other remarkably green children, Rory's as confused by his new condition as the medics seem to be.