Slimeon

Slimeon is a classic example of magical experiments gone wrong. They/them pronouns.
Slimeon's colors and opacity are more of a suggestion, they choose their color and solidity. (Can even be drawn as just a general blob instead of a cat). Slimeon can absorb DNA by touching it and adapt to a form  more like the subject until it's metabolized. They theorize they are not truly their creator (Simon) because of this and are looking for a way to bring him back.