Remember, New Super Mario Bros on the DS and its Mario vs Luigi mode?
Well, some fans liked that mode so much that a new homebrew version has been made that is playable by up to ten people at once.
A description reads as follows:
A unity-standalone 2-10 player remake of the Mario vs Luigi gamemode from the New Super Mario Bros DS download game.
Includes the 5 default levels (Grassland, Bricks, Castle, Pipes, and Ice), along with custom levels: Jungle, Sky, and Volcano! All powerups are implemented and fully faithful to their originals, along with the addition of NSMBWii’s Propeller Suit & Ice Flower!
See some screenshots below
The project is still in beta, but those interested can check it out here. It may be worth downloading before a certain company decides to take action.