Monster Labs

Monster Labs is a video game in which you play a Mad Scientist, creating Mix-and-Match Critters to pit against other similar creatures in turn-based combat. You join Professor Fuseless as his apprentice, and then play through a storyline involving meeting several colleagues of his, fighting an old colleague who did a Heel Face Turn, and saving Innocent Bystanders from monsters. There's also a multiplayer combat mode in which you pit your monsters against other players' monsters.