This is an interesting fan game: it's called New Super Mario Land, and from the name, you can tell it's based on Super Mario Land (GB). Unlike most fan games, this one is made from scratch, which means it's not based on the Super Mario World engine. Since the developer has a reprogrammable Nintendo Power cartridge, he/she is able to copy the game onto it.
The homebrew developer utilised the less-popular New Super Mario Bros graphical style in favour of sprites since he's a fan of prerendered sprites ala Donkey Kong Country and the clean look of the New Super Mario Bros games.
Another notable thing about the multiplayer is that it has four players, and it's basically four Marios with different overalls, based on Mario himself, Luigi, Wario and Waluigi. The developer mentioned that the main challenge is implementing multiplayer since unlike the New games, it doesn't have a zoom function to show more of the screen in case players travelled too far. Not to mention there's maintaining the framerate.
Wario and Waluigi being Scrooge and Marley respectively is brilliant casting, along with Mario and Baby Mario being Bob Cratchit and Tiny Tim. I kind of thought that (King) Boo would have been the better Ghost of Christmas Yet to Come, given how its shadowy nature fits an actual ghost the best. I know Pete was the Ghost of Christmas Yet to Come in Mickey's Christmas Carol, but I think that played out better for being an unexpected character.
Is Luigi supposed to be the character that is Scrooge's nephew? If so, then that's funny.