I have just about zero knowledge on how to go about actually making a game, but thought this would be neat. Player takes control of an octorok. GBC graphics. It'd be more RPG oriented than Zelda games. The player would start with just one move: spitting rocks, and one heart. Leveling up you could add a few stats to evolution, health (each stat gives you a piece of heart), and armor.
Evolution could lead to upgrades like being able to swim, spit rocks farther, stronger rocks (deal more damage), new attack types (like lunge attack or something), and possibly the weirdest one I thought of: # of eggs laid. When you reach an evolution checkpoint for increasing the # of eggs laid, you can have more spawn to fight with!
If you find another female octorok you can mate with them. There'd be certain times when all male octoroks are looking for a mate, so there will be dozens of male competition to kill, and few females. By mating with a female she will follow you around for a bit, and if you protect her and keep her alive she will birth your children. At that point she leaves you, and you have a number of tiny octobabies to fight by your side. They will be small and die quickly, but can swarm enemies and be super helpful and awesome.
When a male notices your female is pregnant, they will try and kill her. It's a rough life for an octorok, but they don't want more male competition, so they kill her only to kill all your unborn spawn. Through evolution you will get abilities to reach new areas with larger, harder enemies. There could even be a town full of Hylian guards. The goal is just to get as many points as you can, by killing things.
Link could even be a random encounter who's really strong and has good A.I., all his items, etc.