Dr. Dometone is one of Third Earth's greatest scientists. He is director and principal guardian of the "Great Oceanic Plug".
Dr. Dometone created two giant frog-like robots called Hercules (a.k.a. Hurkie) and Sampson to help him protect the plug. When the plug was threatened by the salvage man from planet Blue Plunder called Scrape, he came to the surface to enlist the aid of the ThunderCats.