My Life As Invisible Intestines (with Intense Indigestion) is book # 20 in the The Incredible Worlds of Wally McDoogle series. When Wally first becomes invisible (thanks to the handy-dandy OOPS Machine) it's great fun. Now he can do whatever he wants, like defending Opera by humiliating a bully, or helping the local football team come back from a 0-54 score.