Mario & Luigi

Mario & Luigi is a clone of the popular Super Mario Bros game for the NES. The game has an interesting backstory, where the developer Mike Wiering made the game as a programming exercise, and a beta version somehow leaked out and even was taken and sold by another guy! (You can download this alternate version in the "extra files" area above.) The actual game, titled Mario & Luigi later released by Wiering (obviously with no official license from the "Big N") offers decent gameplay and six levels to complete.