Metroid · NES · 1986 · Out of Bounds · Discovered by Community
By exploiting how the original Metroid scrolls between rooms, Samus can leave the intended map entirely and wander through "secret worlds" built from leftover data. Far from a curiosity, the glitch lets speedrunners reach the ending from almost anywhere in the game.
The original Metroid streams its world one screen at a time, loading room data as Samus moves between doors. By manipulating a door transition — typically by passing through it in an unintended way while the game is mid-scroll — players can desynchronise Samus's position from the map the game thinks she is on. Instead of crashing, the game keeps loading whatever data lies beyond the designed boundary, producing a "secret world": a corrupted expanse of garbage tiles, nonsensical room fragments, and platforms that may or may not behave normally. These secret worlds are not just visual oddities. Because the corrupted space connects to arbitrary points in memory, a carefully navigated route through one can drop Samus into the game's final sequence, allowing a run to bypass huge portions of the intended progression. Speedrunners mapped the reliable paths through these regions and built entire categories around them, turning an out-of-bounds glitch into a precise routing tool. The phenomenon is one of the earliest console examples of players treating a game's memory layout itself as navigable terrain.
Metroid loads rooms on demand as Samus moves, keeping only the immediate surroundings in memory. The glitch hinges on breaking the link between Samus's coordinates and the room the game is loading, usually by abusing a door at the moment of a screen transition. Once that link is broken, Samus is effectively standing in space the game never prepared, and the engine fills the screen with whatever data is adjacent in memory.
The result looks chaotic — mismatched tiles, partial rooms, inconsistent collision — but it is deterministic: the same inputs produce the same corrupted layout, which is what makes the secret worlds navigable rather than purely random. Players learned to read these regions as a kind of hidden geography.
Once players realised the secret worlds connected to meaningful parts of memory, the glitch stopped being a novelty and became a routing problem. By charting which movements through the corrupted space lead where, runners found paths that deposit Samus directly into the endgame, skipping the bosses and upgrades a normal playthrough requires.
This turned the original Metroid into an early showcase for memory-aware speedrunning — the idea that a game's internal data layout is itself something a player can traverse. The secret worlds anticipated, on 1980s hardware, the same mindset that later produced credits warps and arbitrary code execution: treat the machine, not just the designed level, as the playing field.