Featuring characters from the Mary Skelter series, Touhou Project, Type;Moon related titles, Digimon, and yes the likes of Super Mario and Pokemon as well as a certain skeleton who banged your mom.
Check out Prism Cross, a fan project created by me and others with an unusual cast of characters to play as with a multitude of modes to check out:
https://prismcross.neocities.org
Besides unlocking the fighters and checking out the overall content, be sure to check out all the possible Trophies you can unlock as well! If you're ever having trouble finding any of that and more out you're more than free to join the Discord server.
With me primarily just being a spriter on the team too, I worked on a good handful of the cast in small ways but primarily had worked on the characters: Mario, Luigi, Gooigi, and Roll of the characters we have shown off publicly. However there is one secret fighter that I was also able to create and is a very special addition (at least in my book).
Best of luck!