My Life as Invisible Intestines (with Intense Indigestion) by Bill Myers

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. Then, of course, there's always giving Wall Street a hand in making her first million. . . . But the fun and games are short lived when everybody from a crazy ghost buster, to the FBI, to the 59 ½ Minutes TV show, to the neighbor's new dog (a cross between a grizzly bear and a Tyrannosaurs Rex) begin pursuing him. Soon Wally is stumbling and staggering through his greatest misadventure ever . . . until he finally learns that cheating and taking short cuts in life are not all they're cracked up to be. Until he learns that honesty really is the best policy.