Penny is Gadget's precocious niece. Always down for the cause, she is a master of investigation and technology who is the one truly responsible for foiling M.A.D.'s schemes, a fact only Brain knows. Using a computer disguised as a book and a utility wristwatch, she monitors her "Uncle Gadget's" activities, communicates with Brain and foils M.A.D.'s plots. Penny very often gets captured by M.A.D. agents before calling Brain for help or escaping by herself.