From his first year, Ben's parents assiduously provide him with homemade Halloween costumes—clever, but usually casting him as sidekick to older brother Michael (rabbit to his magician or angel to his devil) and not always comfortable—the wooden cheese wedge (Michael is a mouse) is too heavy and the robot (paired with its scientist creator) too hot inside. Finally, at seven, Ben sensibly declares his independence and makes his own costume: he's ``an intergalactic-space-starship robotron armed with a laser-pulverizer-beam rod,'' simply and comfortably engineered from one paper bag and two paper-towel rolls. A mildly satirical story that amusingly reflects realistic child development. Meddaugh's bright, cartoony art nicely extends the action and humor. (Picture book. 3-7)