World D is the fifth and final secret world that was featured in the game Super Mario Bros.: The Lost Levels, following World C. Like the other secret worlds, it was left unused in Super Mario Bros. Deluxe. When Bowser is defeated at the end of World D-4, Princess Peach is saved, and, as such, Mario and Luigi beat the game.
This level is a similar level to World 8-1. In the original FCD version, it is a snowy level, but in the SNES remake, its a grassy level.
This level includes several upside down Piranha Plants.
This level has a brick wall in the background similar to World 8-3. In Super Mario All-Stars the wall is gone so the brick blocks are replaced with hidden blocks.
This castle level is a castle which starts out like World 8-4, but there are only 5 Fire Bars that Mario or Luigi need to avoid.