Polysaurus Rex is a character that appears in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. It was a two-headed dragon that was thought to be extinct. It guarded two doors in the Forbidden Zone
Described as a "bio-mechanical watchdog", one of its heads would always tell the truth, whilst the other would only tell lies, though it was impossible to discern which one beforehand. Sally Acorn encountered it whilst on her soul-quest from Julayla Chipmunk and was able to outsmart it.