The Rainys
The concept of a rainy is as old as time, literally. when the Multiverse was created rainys came along with it, acting as a justice and/or crimefighting service for anything not quite right in the Multiverse be it wriggling rodents, pesky birds, or more such things in the wrong place.
Rainys are mainly known for their shapeshifting abilities. being able to take any possible shape , as well as increase/decrase their mass, and all at will. it made them a powerful force. An offshoot of their shapeshifting powers are clones, because they can just make more mass they can make more of themselves. There was just one rainy originally, and wow did he clones.
THIS Rainy
A long long time ago, a rainy was struggling in a low level chase against an interdimentional rodant, he was attempting to create all kinds of objects to catch it, so many that he accidentally made a clone. The clone was very quickly discarded however, so quickly that he barely developed at all. The "clone"(which was currently nothing more than a colorful blind slug) fell into a void, a place with no start or end, besides the floor. He was left slugging around in an endless hall of white, slowly collecting dust and leftover nutrients, slowly progressing and growing. eventualy he had enough matter to think, he creates some eyes to see through using a newfound power to shapeshift, he spends many long years developing himself, learning his porpose and powers.
using his powers, rainy creates a new mechine that allows him to travel through worlds, going through many a misadventures and earning nice friends and becomeing a super rainy later on cuz he saved the worlds