Leo Cockroach... Toy Tester

""Testing toys is hard work, and it can be downright dangerous for a cockroach,"" according to this humorous tale of a misunderstood insect. However, Leo Cockroach loves his job. By night, wearing pince-nez and toting a clipboard, the amiable fellow samples prototypes of games, dolls and remote-control vehicles. With help from his assistant, a tawny cat named Bernard, Leo puts his favorite finds in the office of Mildred Splatt, ""president and CEO of Waddatoy Toys."" Unfortunately, Mildred doesn't know who selects these sure-fire hits, and thus views Leo more as cootie than collaborator. After one too many near-squishings, the insulted Leo defects to Notsogouda Toys, a rival company across the street. O'Malley's (Velcome; The Candy-Store Man) zany humor is at its best here, especially when inventing products for Leo's perusal. Leo straps on goggles to fly tiny planes and, clad in a green lab coat, he stares askance at duds like the ""stringless yo-yo"" and ""Baby Boom: Babies' First Fireworks."" Though some readers will wonder why Leo waits so long to reveal his identity as top toy spotter to Mildred, most will be thoroughly entertained by O'Malley's wry episodes and evocative pencil-and-watercolor images, which offer a comical new perspective on micro-level R&D. Ages 5-8. (Mar.)