World 5 (Super Mario Bros.)
World 5 is the fifth world of Super Mario Bros.. World 5 introduces a new enemy, the Bullet Bill, along with the Bill Blaster. This world features shorter time limits and harder levels. Levels, though, start to repeat from this world on, only with increased difficulty.
 World 5-1
This is the first level to introduce the Bullet Bill. This level contains numerous amounts of gaps, as well as a good abundance of Bullet Bills, Goombas, Koopas, Koopa Paratroopas; Piranha Plants also appear in every pipe in the level as usual. Many Brick Blocks are found throughout the level as a sort of alternate road, and in some circumstances a platform to avoid being harmed.
 World 5-2
This level is yet again a ground level. It has a lot of the same features as the previous level, only it is laid out different. Bullet Bills, Goombas, Koopas, Hammer Bros, Bloobers, Cheep-Cheeps and Piranha Plants are once again found in this level. Also, Buzzy Beetles are found in this level; This is the first level that features Buzzy Beetles on above ground, rather than underground.
 World 5-3
This level is once again set at great heights. This level is exactly the same as World 1-3, only with smaller moving platforms and Bullet Bills flying across the screen (though it is unknown where they come from).
 World 5-4
The last level of World 5 is, of course, a castle level. This level is exactly the same as world 2-4 only it features more and longer firebars. More podoboos are in this level as well. Another False Bowser is found at the end of this level, as well as another Mushroom Retainer. The player must go on to the next world to find Princess Toadstool.