Template:FeaturedRandom/Super Mario World
Released: 1990, SNES
It contains a wealth of unused levels, some of which are from extremely early in development. There's also a lot of unused objects, from a classic Piranha Plant to a ceiling full of Swoopers – all the way to an unused screen-sized cage!
All this, combined with a lot of interesting early graphics from the SNES Test Program, the SNES Burn-In Test Cart, and magazine preview screenshots, reveals that Super Mario World was originally intended to be a very different game: Super Mario Bros. 4.