Every video game has bugs. Most are boring: a texture flickers, a character clips through a wall, a frame drops. But every few years, a bug comes along that is so weird, so reproducible, and so embedded in the culture that it becomes part of the game’s identity. Players build entire communities around it. Researchers cite it. Documentary films get made about it.
This list pulls ten of the strangest bugs in video game history, runs each one through Wikipedia, Bulbapedia, Halopedia, or a developer interview, and explains what caused the bug, what players did with it, and whether it ever got fixed. If you like this kind of thing, our 12 strange Pokemon facts that are actually true follows the same sourcing rules, and our 20 facts that sound fake but are true with sources covers the same ground for non-gaming facts.
On this page
- How We Picked These Bugs
- Bug 1: MissingNo (Pokemon Red and Blue, 1996)
- Bug 2: The Corrupted Blood Plague (World of Warcraft, 2005)
- Bug 3: The Minus World (Super Mario Bros, 1985)
- Bug 4: Pac-Man Kill Screen (Pac-Man, 1980)
- Bug 5: The Skyrim Space Program (Skyrim, 2011)
- Bug 6: Sonic’s Debug Mode (Sonic the Hedgehog, 1991)
- Bug 7: Halo 2 Super Bounces (Halo 2, 2004)
- Bug 8: Donkey Kong Kill Screen (Donkey Kong, 1981)
- Bug 9: The Hot Coffee Mod (GTA San Andreas, 2004)
- Bug 10: The Nuclear Gandhi Myth (Civilization, 1991)
- More Gaming Rabbit Holes
- Sources
How We Picked These Bugs
Three rules before any bug made the list. It had to be real and reproducible, not a rumor or a creepypasta. It had to be weird in a way that went beyond “the game crashed,” meaning it produced unexpected in-game behavior that players actually used or memorialized. And it had to be sourced to a primary document, meaning Wikipedia, a franchise wiki (Bulbapedia, Halopedia, Mario Wiki), a developer interview, or a verified datamine.
We also explicitly included one bug that turned out to be a myth, the so-called Nuclear Gandhi glitch from the original Civilization, because debunking it is more interesting than repeating it. Most lists of video game bugs still include Nuclear Gandhi as a real bug. Sid Meier himself confirmed in 2020 that it never happened, and the real story is a useful lesson in how gaming myths spread. If you want more verified-but-strange gaming history, our 12 strange Pokemon facts that are actually true follows the same sourcing rules.
Bug 1: MissingNo (Pokemon Red and Blue, 1996)
MissingNo is the most famous video game bug of all time, and the reason an entire generation of kids learned the word “glitch.” It was a Pokemon that did not exist, with a sprite made of broken tiles, that appeared only if you performed a very specific sequence of actions in Pokemon Red and Blue.
The recipe, as documented on the Bulbapedia old man glitch page, was simple in execution and absurd in implication. You talked to the old man in Viridian City who teaches you how to catch Pokemon. You watched his demonstration. You flew to Cinnabar Island. You surfed up and down the eastern coast, on the strip of water that the game treated as a wild Pokemon zone but never populated with actual Pokemon. After a few seconds, MissingNo appeared.
What was actually happening under the hood is a memory overflow bug. The game stored the player’s name in a temporary buffer during the old man tutorial, then loaded the Cinnabar coast as a wild encounter zone without resetting the buffer. The game tried to read the player’s name as a list of Pokemon IDs, and if your name had the right characters in the right positions, you got MissingNo, whose internal ID was 0. Catching MissingNo corrupted the player’s inventory in a specific way: the sixth item in your bag would duplicate to 128 copies. This was the most reliable item duplication glitch in the game, and it is the real reason kids did the MissingNo trick. The Pokemon itself was a side effect.
MissingNo was never patched out of the original Red and Blue cartridges, because cartridge games cannot be patched. It was fixed in the Spanish and Italian versions of the game by making the Cinnabar coast tiles act as water tiles, according to Bulbapedia. The Virtual Console re-releases on 3DS in 2016 still had the glitch, because Nintendo deliberately preserved it as a feature of the original experience.
The Pokemon Company eventually embraced MissingNo as a piece of franchise history. It has been referenced in trading card sets, manga, and even in later games as an Easter egg. Not bad for a programming oversight.
For anime-side Pokemon errors instead of cartridge glitches, see our Pokemon anime mistakes list, which covers dub name swaps, continuity goofs, and the black-tail Mandela Effect with sources.
Bug 2: The Corrupted Blood Plague (World of Warcraft, 2005)
In September 2005, World of Warcraft accidentally became the site of one of the most studied virtual pandemics in history. The bug, called the Corrupted Blood incident, was so influential that epidemiologists later used it as a model for real-world disease spread.
Here is what happened. On September 13, 2005, Blizzard released the Zul’Gurub raid, whose final boss, Hakkar the Soulflayer, cast a debuff called Corrupted Blood on players. The debuff dealt 263 to 337 damage every two seconds and was supposed to spread to nearby players, but only inside the raid. The intent was that the debuff would expire when the player left the raid, or when the player died.
The bug was that the debuff did not expire for pets and non-player characters. Hunters and warlocks could dismiss their pets while the pet was infected, then summon the pet in a crowded city like Ironforge or Orgrimmar. The pet would still be infected. The infection would then spread to nearby players, including low-level characters who could not survive the damage.
Wikipedia’s entry on the Corrupted Blood incident confirms the timeline. The plague spread across multiple servers within hours. Bodies piled up in major cities. Players who could heal tried to help. Some players intentionally spread the disease, roleplaying as bioterrorists. The game’s economy briefly collapsed as people abandoned cities for the countryside. Blizzard tried to quarantine infected zones, but players kept spreading the debuff through pets and through the auction house.
The fix, deployed on October 8, 2005, according to Wowhead, was a hotfix that made Corrupted Blood affect player pets correctly. But by then the incident was already famous. In 2007, epidemiologist Nina Fefferman published a paper in The Lancet Infectious Diseases arguing that the Corrupted Blood incident was a useful model for real-world disease spread, because players behaved with the same mix of panic, altruism, and malice that real humans show during outbreaks. The paper has been cited hundreds of times, and the incident was revisited widely in 2020 during the early months of COVID-19.
Bug 3: The Minus World (Super Mario Bros, 1985)
The Minus World is one of the oldest intentionally reproducible bugs in console gaming. It is a level in Super Mario Bros that does not exist in the game’s level data, but players can enter it through a specific exploit in World 1-2.
The recipe, as documented on the Mario Wiki Minus World page, requires precise movement. In World 1-2, you reach the end of the underground section without entering the warp zone pipe. You jump onto the ceiling just before the pipe that exits the level. You walk backward past the pipe to trigger the warp zone’s three pipe destinations, but you do not scroll the warp zone fully onto the screen. You enter the leftmost pipe before its destination value loads correctly. The game then sends Mario to World -1, rendered in the HUD as a negative number because the value underflowed.
The Minus World is an underwater level, layout-wise identical to World 2-2 but with a critical difference: the pipe at the end of the level has no destination set, so entering it sends you back to the start of the same level. You can play it forever. Wikipedia notes that on the original Japanese Famicom Disk System version, the Minus World was a different, completable level, because the disk version loaded level data differently. The international cartridge release locked players into an infinite loop.
The Minus World became one of the first widely shared playground rumors in console gaming. Kids passed the recipe around by word of mouth, magazines published it, and Nintendo eventually acknowledged it in interviews. It is one of the reasons the speedrun community still revisits Super Mario Bros, because the bug reveals how the game’s level loading actually worked under the hood.
Bug 4: Pac-Man Kill Screen (Pac-Man, 1980)
If you play Pac-Man long enough, the game breaks. Specifically, if you reach level 256, the right half of the screen fills with broken symbols and the level becomes impossible to complete. This is the Pac-Man kill screen, and it is one of the most famous integer overflow bugs in computing history.
The cause is the way Pac-Man stores the level number. The game uses a single 8-bit byte to track the current level, which means the maximum value is 255. When the game tries to draw the fruit counter for level 256, it draws 256 fruits, which overflows into adjacent memory and corrupts the level rendering. Half the screen becomes a mess of broken tiles. There is no way to win.
Wikipedia confirms this was an integer overflow bug. Toru Iwatani, the creator of Pac-Man, did not expect anyone to reach level 256, because the game becomes extremely difficult well before that point. Reaching the kill screen legitimately requires hours of perfect play and is considered one of the classic achievements in arcade gaming. The Pac-Man Wiki Map 256 Glitch page covers the same overflow in more detail, and the documentary Chasing Ghosts: Beyond the Arcade features players who achieved it.
The Pac-Man kill screen is also famous for inspiring the broader concept of kill screens in classic arcade games. Donkey Kong had one. Qbert had one. Many early arcade games had integer overflow bugs at level 256 or similar thresholds. The phrase kill screen entered the gaming vocabulary through Pac-Man and Donkey Kong, and is now used to describe any level where a game becomes impossible due to a programming limitation.
Bug 5: The Skyrim Space Program (Skyrim, 2011)
When Skyrim launched in November 2011, players quickly discovered that if a giant hit you with its club and you died, your character’s body would be launched hundreds of feet into the air. The community named it the Skyrim Space Program, and the bug became one of the most-shared launch-week memes in modern gaming.
The cause is in the physics engine, not the combat system. Skyrim uses the Havok physics engine, and giant attacks apply a force value to the target. When the target dies, the game’s death animation interacts with the applied force in a way that multiplies it. The result is that a killing blow from a giant sends the player’s ragdoll corpse flying into the sky, often past the cloud layer.
This was not a small bug. It affected almost every player who encountered a giant in the first hours of the game, because giants hit hard enough to one-shot most low-level characters. GameFAQs threads from January 2012, the month after launch, document players debating whether it was intentional or a glitch. The consensus, eventually confirmed by Bethesda developers in interviews, was that it was an unintended interaction between the physics engine and the death animation, and that fixing it cleanly would have required rewriting how physics forces applied to dead actors.
The bug was never fully fixed in the original Skyrim release, and it persisted into the Special Edition re-release in 2016. Modders eventually released unofficial fixes on Nexus Mods that reduced the launch height. But the Skyrim Space Program became such a recognizable part of the game’s identity that many players consider it a feature. It is one of the few bugs on this list that the community actively resisted fixing.
Bug 6: Sonic’s Debug Mode (Sonic the Hedgehog, 1991)
Debug mode is not exactly a bug, but it is a programming oversight that became one of the most beloved cheat codes in console gaming. The Sonic the Hedgehog debug mode gives players godlike control over the game: they can place any object anywhere, fly through levels, and become invincible.
To activate debug mode in the original Sonic the Hedgehog on Sega Genesis, you enter a sequence on the title screen: hold A, press Up, Down, Left, Right, then press Start while still holding A. According to the Sonic Wiki Debug Mode page, this opens the level select screen. From there, you select the Sound Test option and play a specific sequence of numbers: 01, 09, 09, 01, 00, 06, 02, 03. If you enter it correctly, you hear a ring collect sound, and debug mode is now active. Eurogamer’s Sonic Origins cheat codes guide also documents how the tradition carried into later re-releases.
What is interesting about debug mode is what it reveals about how the game was built. The level select menu and the object placement system were developer tools, used during testing to jump to any level and place any object without playing through the game normally. They were never meant to ship in the consumer version. But Sega left them in the code, accessible through a specific button combination, and players discovered them within months of the game’s release.
The Sonic Wiki notes that similar debug modes exist in Sonic 2, Sonic 3, Sonic and Knuckles, and Sonic CD. Each has its own code, but the underlying concept is the same: developer tools left in the shipping game, discoverable by players. Debug mode became a tradition in the Sonic series, and modern games like Sonic Mania deliberately include it as a fan service. It is one of the few oversights that became an official feature because players loved it so much.
Bug 7: Halo 2 Super Bounces (Halo 2, 2004)
Halo 2 multiplayer in 2004 and 2005 had a bug that became a subculture of its own. Super bouncing, or super jumping, let players reach absurd heights on multiplayer maps by exploiting a specific interaction between crouching, terrain geometry, and the game’s physics.
The recipe, as documented on Halopedia’s super jumping page, varied by map. On Containment, you crouched into a specific corner of a wall, walked forward while still crouched, then jumped out and immediately let go of crouch. If you did it right, you launched hundreds of feet into the air, often landing on top of buildings or outside the playable area. From up there, you could shoot down at other players with a sniper rifle, and they could not hit you back.
What was happening was a collision detection bug. The game’s physics engine, when a crouched player clipped into a wall at a specific angle, would apply a corrective force to push the player out. If the player released crouch at exactly the right moment, the corrective force was applied with no clip resistance, launching the player upward.
Super bouncing was a competitive advantage, and it divided the Halo 2 community. Some players considered it cheating and refused to use it. Others built entire match strategies around it. Bungie never patched it in the original Xbox release, partly because patching console games in 2004 was logistically difficult and partly because the community had come to accept super bouncing as part of the game’s identity. According to Halopedia, the bug was removed in the PC port, Halo 2 Vista, in 2007, and was not present in the Halo: Master Chief Collection version, except in the dedicated Classic mode.
Bug 8: Donkey Kong Kill Screen (Donkey Kong, 1981)
The Donkey Kong kill screen is the most famous kill screen in arcade history, partly because of the documentary King of Kong: A Fistful of Quarters, which followed Steve Wiebe’s attempts to break the world record on the game.
The bug appears at level 22, or more accurately, at the 117th screen of the game, which the game’s internal counter labels as level 22. At that point, the game’s timer, which is supposed to count down from a value determined by the level number, becomes shorter than the time it takes to actually play the level. The timer hits zero before Mario can reach the top of the screen, and the player dies. There is no way to beat level 22. The game is effectively over.
Unlike the Pac-Man kill screen, which is a rendering bug, the Donkey Kong kill screen is a balancing oversight. The game’s designers did not expect anyone to reach level 22, because the difficulty ramps aggressively and the typical arcade session in 1981 lasted maybe 10 minutes. But expert players who could survive long enough to reach level 22 discovered that the game simply ran out of time for them.
Wikipedia notes that the phrase kill screen entered the broader gaming vocabulary largely through Donkey Kong. The 2007 documentary King of Kong made the kill screen famous outside arcade circles, and the scene in which Brian Kuh announces a kill screen is coming up at Funspot arcade became one of the most-quoted moments in gaming documentary history. Steve Wiebe’s kill-screen runs, which always ended at that hard stop, are now considered a foundational moment in competitive gaming.
Bug 9: The Hot Coffee Mod (GTA San Andreas, 2004)
The Hot Coffee mod is technically not a bug in the traditional sense, but it is one of the most consequential pieces of unused code in video game history, and the controversy it triggered reshaped how the entire industry handles cut content.
Here is what happened. In 2004, Rockstar Games released Grand Theft Auto: San Andreas. The game included an adult relationship minigame nicknamed Hot Coffee. The minigame was cut from the final release, but the code and assets were left on the disc, with the girlfriend’s coffee invitation leading to a fade-to-black instead of the minigame.
In June 2005, a modder named Patrick Wildenborg released a mod for the PC version of San Andreas that re-enabled the Hot Coffee minigame. The mod did not add new content. It simply unlocked the code Rockstar had left on the disc. Wikipedia’s entry on the Hot Coffee minigame confirms this distinction: the content was already in the game files, just inaccessible without modification. Eurogamer’s Hot Coffee investigation remains one of the clearest timelines of how the controversy escalated.
The controversy was explosive. Rockstar initially claimed the mod added the content, but the modding community proved the assets were on the original disc. The Entertainment Software Rating Board (ESRB) re-rated San Andreas from Mature to Adults Only, the first time a major game had been re-rated after release. Major retailers pulled the game from shelves. The US House of Representatives voted 355 to 21 to authorize a Federal Trade Commission inquiry into Rockstar. Take-Two Interactive, Rockstar’s parent company, settled with the FTC in 2006 for an undisclosed sum.
The Hot Coffee incident is one of the reasons modern games are more careful about leaving cut content on the disc. It also accelerated the industry shift toward digital distribution, because digital games can be patched to remove content after release, whereas physical discs cannot. The whole saga started because a developer left unused code on the shipping disc, which is a quiet kind of bug with very loud consequences.
If you liked the Hot Coffee story as cut content that still shipped, our bizarre things found in video game code list covers more dataminer finds, and our 15 lost video games you’ll never get to play covers projects that never shipped at all.
Bug 10: The Nuclear Gandhi Myth (Civilization, 1991)
The final entry on this list is not a real bug. It is a myth that nearly every weirdest video game bugs list still repeats as fact, and debunking it is more interesting than repeating it would be.
The story goes like this. In the original Civilization, released in 1991, each leader had an aggression rating from 1 to 10. Gandhi had the lowest, at 1. When a leader adopted the democracy government type, their aggression rating dropped by 2. If Gandhi adopted democracy, his aggression would drop from 1 to -1. Because the aggression value was stored as an unsigned 8-bit integer, -1 rolled over to 255, the maximum possible value. Gandhi, the most peaceful leader in the game, would suddenly become the most aggressive, and would start using nuclear weapons liberally.
The story has been repeated for over a decade. It appears in YouTube videos, Reddit threads, gaming blogs, and several books. There is just one problem. Sid Meier, the creator of Civilization, confirmed in his 2020 autobiography that the bug never existed.
Wikipedia’s entry on Nuclear Gandhi documents the debunking in detail. According to Meier, the original Civilization did not use an integer for aggression in the way the story claims. Aggression was a value from 1 to 3, not 1 to 10, and the game’s code did not have the kind of overflow the story describes. Gandhi’s tendency to use nuclear weapons in later Civilization games, which is real and observable, was added deliberately by developers as a nod to the original myth. The myth became the feature.
Why does the myth persist? Because it is a great story. A bug that turns the most peaceful leader in history into a nuclear warmonger is funnier than the truth, which is that Gandhi just nukes you because the developers thought it would be funny. The Nuclear Gandhi myth is one of the best-documented examples of how gaming folklore can override the actual history, and it is the reason we put it last on this list, as a warning about how easy it is to repeat a good story without checking it.
If you enjoyed this kind of debunking, our 12 strange Pokemon facts that are actually true explicitly excludes popular myths like the Ditto-Mew clone theory for the same reason.
More Gaming Rabbit Holes
If you read this whole list and want more, here are a few directions to go.
- TASVideos, the home of tool-assisted speedruns, has documentation of thousands of glitches used to beat games faster than humanly possible. The Pokemon Red any-percent run, which uses a glitch to reprogram the game’s memory and write a win condition directly, is one of the most-watched TAS videos on YouTube.
- The Cutting Room Floor, a wiki dedicated to unused content in video games, is the source of much of what we know about debug modes and cut content. The Hot Coffee entry is particularly detailed.
- Speedrun.com hosts leaderboards for hundreds of games, and the glitch explanation threads on each game’s forum are a goldmine of well-documented bugs.
- Our 12 strange Pokemon facts that are actually true covers franchise weirdness with the same sourcing rules.
- Our 20 facts that sound fake but are true with sources follows the same sourcing rules for non-gaming facts.
- If you want to play something instead of reading about it, our 20 best free PC games that run on a potato (2026) includes several classic open-source games with their own hidden debug modes and cheat codes.
- Prefer encyclopedia deep dives? Start with our 50 Wikipedia rabbit holes.
- Want cut content and developer messages instead of runtime glitches? Our bizarre things found in video game code by dataminers list covers Hot Coffee, Gaster, Apex job listings, and more.
Sources
- Old man glitch, Bulbapedia
- Missingno, Glitchipedia
- Cinnabar Island wild Pokemon glitch, GameFAQs
- Corrupted Blood incident, Wikipedia
- Corrupted Blood (debuff), Warcraft Wiki
- The Corrupted Blood Incident Began Sixteen Years Ago, Wowhead
- Minus World, Wikipedia
- Minus World, Mario Wiki
- Pac-Man, Wikipedia
- Map 256 Glitch, Pac-Man Wiki
- Nuclear Gandhi, Wikipedia
- Hot Coffee (minigame), Wikipedia
- Who Spilled Hot Coffee, Eurogamer
- Debug Mode, Sonic Wiki Zone
- Sonic Origins cheat codes, Eurogamer
- Super bouncing, Halo Alpha
- Super jumping, Halopedia
- Steve Wiebe playing Donkey Kong Kill Screen, YouTube archive
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