I had a stray thought about what it must feel like to be a fish and now suddenly the entire planet is an ocean. I'll try to fix it in a second, at the moment I'm trying to think about how not to drown.

Really, superpowers need a lot of caveats or it's just horrible. Even in comics / cartoons people don't have the knowledge and responsibility to use their powers properly. But, at least those people are given super-endurance and massive plot armour along with their powers.

If someone could change reality at your will, could their puny human brain manage such an enormous power? If someone could shapeshift, could their modified body put up with the stresses of that new shape? Does having the shape of a bird give you a bird's ability to fly -- not just the knowledge but the hollow bones, etc? If someone had super strength, would it follow that they have super skin that won't rip and tear if they punch a wall? If someone could fly, would they run out of oxygen at 10km height? Would they be able to fly up there without freezing?