Suburban Beasts

Suburban Beasts is a fighting/adventure game released in 1992.

Gameplay
You get to choose between two characters, an anthropomorphic porcupine or an anthropomorphic cat beast. Both were previously human before they were mutated as part of a sadistic experiment. They intended to work together, but their primal urges took them over and now they resort to fighting each other.

The game acts as a side scroller, and you'd get to face whomever you don't choose to play every now and again.