This is Super Smash Land, the Game Boy release of Nintendo's bestselling brawler that never existed until now. And, yes, that's Kirby and Mario duking it out at Peach's Castle in monochromatic glory.
Super Smash Land is the creation of digital artist Dan Fornace, writes Piki Geek, an 8-bit de-creation that manages to squeeze good-natured mascot-on-mascot violence onto a d-pad and two buttons. It's not actually made for the Game Boy—don't fire up that emulator just yet—but an interpretation of how a Smash Bros. game released in 1990 would look.
The de-make is being built by Fornace in Game Maker 7, so you'll play it on your PC whenever (if ever) it's released. Ultimately, four-player support is planned with appearances from Mario, Kirby, Link and Pikachu in the small roster.
This is Super Smash Land in action.
Super Smash Land: A GameBoy De-make [Piki Geek - thanks, DAC!]