I'm working on something that's basically a spiritual successor/love letter to digimon. Working titles are eCreecherz or mon.ster. I'm hoping to find a way to make it GM-optional. PCs meet monsters that they design the basics of, and through adventuring, scenarios, and battles, their bond grows, changing the ways a monster could possibly evolve. PCs and mons alike will have personality traits, flaws, fears, goals, etc, that are used for jumping off points for role-playing.
there will be goofy and, optionally, random way your mon can evolve, pulled from different tables, anything from increasing in mass and height, growing horns, or they just have shorts and a gun now.
bond level and actions towards the world and your monster will influence how they behave in combat, as well as your influence over it. I do want combat to move fairly quickly though, and not dominate the game experience. Like the show it's based on, I aim to have the core of the experience be about personal growth for the PC and the monster through interpersonal and in-universe conflict.