What if you took New Super Mario Bros for the Nintendo DS and hacked a complete recreation of Super Mario 3 into the thing? Well, why stop there? Why not put some Metroid and Legend of Zelda in there too?
Well, someone did that, creating the hacked New Super Mario Bros 3, which not only puts recent Mario powers like the ability to shrink and wear a blue Koopa shell into classic NES era levels, the fan-made game also injects tons of bonus content. There are Metroid-themed zones, classic levels from Super Mario Bros 2 and much much more.
New Super Mario Bros. 3 [Final Trailer] [YouTube - Thanks Reducks!]