Part of the Minus World level. As it is seen, under the "world" sign, it says "-1".
|First game||Super Mario Bros. (1985)|
Minus World is a glitch level in Super Mario Bros., but was fixed in subsequent releases in titles such as Super Mario All-Stars and Super Mario Bros. Deluxe, but was kept in the Classic NES Series version. The Minus World is among the most popular glitches in video games. It is actually level 31-1; although the 31st identifier for characters in Super Mario Bros. is denoted as a space, hence the stage appears as level " -1".
This level is an underwater level like in World 2-2 with the same geography and enemies, although it cannot be completed because the pipe at the end of the level brings the player back to the beginning of the stage.
In order to access the world, you must perform a glitch to go through a wall, typically in World 1-2 at the end of the underground section. In order to accomplish this, you must jump backwards as large Mario off of the sideways portion of the pipe, toward the wall, while crouching. You then must stop crouching as soon as you hit the ceiling, being careful not to hit the wall. If you have done this correctly, you should slide right through the wall. Then, you must go through the farthest left pipe, warping you to the Minus World. There are two glitches that make this possible. First, being able to slide through the wall is due to an oversight in the physics, but the pipe's warp is actually because of the default warp zone being for worlds 31, 5, and 31. This layout is used in the game at the end of the underground part of World 4-2, although the pipes that would lead to World 31 are missing. Normally, you would only see the 4, 3, 2 warp zone in 1-2 because the game will load that warp zone in when you walk toward the small hole in the ceiling that you would usually use to enter the room. Because you go through the wall, this is never loaded, leaving the default 31 5 31 warp zone in.
- The secret and intentional World 9 in Super Mario Bros. 2: The Lost Levels was actually inspired by the Minus World.