These were the monsters in the Mutant Mania traveling circus. They include: Medusa, Giant Gila Monster, Scorpio and several other unnamed monsters, such as a horned toad-like creature and a rodent-like monster.
A mutated anemone found on a pacific atoll by mutant circus owner Tobias Wilson, the creature, dubbed Medusa by her captor, was put on display for the circus to enjoy. On one such show in New York City, Medusa got free by turning into a liquid form. H.E.A.T., whom was watching with Tobias, was quickly on the offensive and soon the mutant was on the rampage, draining people dry. While her victims were revived with massive amounts of water, the creature continued on, wading through military might unlike that of any other.
After being forced to melt, she entered the subway system and then the water reservoir. The electric fence only made her melt yet again and she entered the city water supply and quickly began to grow. Godzilla arrived just in time to fight, but his atomic fire made her melt and cover him, draining him dry also. She escaped and left Godzilla for dead.
She made it out to sea, but Godzilla, revived thanks to H.E.A.T. and the military, was again on an attack. He repeatedly blasted the anemone, preventing her from reshaping or even making an attempt to strike again. When Nick called him back, the Heat-Seeker quickly moved in, sucking up the liquidated Medusa with a huge vacuum meant to clean up oil spills. With heated coils inside, Medusa was trapped inside. What ever happened to her remains unknown.
Giant Gila Monster