Grybyx

The Grybyx was an extremely cute creature vaguely resembling a bipedal platypus from Dimension X, owned by the Neutrinos- when it fed upon Earth foods, it mutated into a monstrous, bear-like creature. The transformation could be undone by exposure to water.

References

• Teenage Mutant Ninja Turtles: "The Grybyx" (1989)