Back in 2011, I wrote about a project called Newer Super Mario Bros. Wii, in which a group of fans were making their own sequel/expansion for the Wii platformer.
https://lastchance.cc/bedroom-coders-making-new-super-mario-bros-wii-sequel-5799838%3C/a%3E%3C/p%3E
Newer adds 128 new levels, has new bosses, visual tweaks and a whole host of other stuff.
Itās free to download, of course, and can even be played on unmodded Wiis, but youāll need a copy of the original New Super Mario Bros. Wii for it to work.
Newer Super Mario Bros. Wii [Site]