Wacko was an alien criminal who sought to destroy the universe using seismospheres. He was a member of a species capable of altering their body structure. In his "normal" form he was small and cute, but he could cause himself to grow huge and muscular and even stretch his body out. Captured by Captain Big Nasty of the Outer Space Patrol, he was fitted with a collar that prevented him from bulking up, and also from speaking. Wacko escaped and stole the seismospheres and fled to Earth. Found by Drake and Gosalyn Mallard and Honker and Tank Muddlefoot coming home from the theater, he was adopted by Gosalyn as a pet.
With her help he was able to get the restrictive collar off, and reacquire the seismospheres which had been found and kept by Tank, who mistook them for jawbreakers. Wacko then more or less kidnapped Gosalyn and Honker and held them hostage, threatening to use the seismospheres, but he was stopped by the combined forces of Darkwing Duck and Captain Big Nasty.