Foaster

TL;DR

A universe was born and a god was born with it, this god was taught by other gods what the duties of a god and its universe are and what stuff isn't allowed to be done (and also why not).
This freshly born god with his freshly born universe soon saw the beauty of space and immediately chose to make itself look like what he was seeing at the moment.

Many centuries after that a world caught his attention and started to peek on it now and then to see what the mortals were doing, and one day they suddenly had created a squishy, animal-looking toy filled with air that they used to have a blast on water!

It was so nice and fun that he chose to let himself be one of those toys, he chose to be a shark because that way he was edgy and sly and soft and fun at the same time.

Many millenia have passed and now Matthew is the equivalent of an adult god, he hasn't changed much since he always quite enjoyed the idea of being a galaxy shark