Super Mario Crossover is a version of the original Mario Bros Nintendo game that allows you to play as characters from other classic NES titles.
You can choose to play Super Mario Crossover as one character, or elect to change characters after every level. There are seven different characters to pick from: Mario (obviously), Samus (from Metroid), Mega Man, Link (Zelda), Simon Belmont (Castlevania), Ryu Hayabusa (Ninja Gaiden), and Bill R (Contra). Each has its own moves and control system, based on how the behave in their original game. You'll soon find out that these other characters are generally much better at Super Mario Crossover than Mario is!
In terms of both gameplay and presentation, Super Mario Crossover has been lovingly recreated from the original 8-bit Mario Bros game on the NES. This means you get cutesy graphics (though very, very retro by today's standards), simple game controls, and a whole lot of fun.
Perhaps the most annoying thing about Super Mario Crossover is the fact that you can't play it at full screen, and are restricted to a fairly small gaming window. This makes it difficult to kid yourself that you're playing on an old games console.
Super Mario Crossover brings an interesting new element to the Mario Bros formula with the inclusion of some of the forgotten heroes of the Nintendo Entertainment System.