Dr. Fossil is a paleontologist who worked at the natural history museum in St. Canard until, for reasons best known for himself, he turned himself into a humanoid pteranodon using his invention, the Retro-Evolution Gun. He later did the same to Stegmutt, the museum janitor, and Stegmutt became his unwitting henchman. It is not known precisely why Fossil de-evolved himself into a pteranodon, but his new form made him an outcast among the other animals in St. Canard, and he began to resent their stares, jeers, and cries of, "Look! It's Godzilla!" He also began to see that, to modern people, dinosaurs were nothing but a source of entertainment and amusement. Fossil began plotting to bring about the end of the world.
Fossil sends Stegmutt to abduct tax attorneys Shyster and Loophole to use as test subjects for his Retro-Evolution Gun and to make them part of the select few de-evolved people who would survive the cataclysm alongside himself and Stegmutt. This attracted the attention of Darkwing Duck. Sort of. While Darkwing suspects that Shyster and Loophole have been kidnapped on the order of their former client, Numero Uno, Gosalyn and Honker follow Stegmutt's footprints back to the museum where they encounter him and then Dr. Fossil and the de-evolved Shyster and Loophole. Stegmutt shows them Fossil's underground lair, and Fossil imprisons the two in a cell after explaining his plan to destroy the world. He then sends Stegmutt to Camp Canard to steal a super-magnet, with which he plans to bring down the passing Cleanser Comet and recreate global extinction, only with modern people and not dinosaurs.
Darkwing, having hit a dead end with Numero Uno, is on his way home when he encounters Stegmutt stealing the magnet, and thus makes it his business to thwart Fossil's evil scheme and rescue Gosalyn and Honker. He accomplishes neither and gets zapped with Fossil's Retro-Evolution Gun and turned into a skyscraper-sized half duck, half dinosaur, and Fossil's plan is foiled when Stegmutt turns against him and realigns the magnet. This sends the comet away from Earth, but also attracts a variety of metal things, including a ship which slams into Fossil and knocks him unconscious. He is last seen, dazed, tied up on the museum rooftop.