Hidden secrets, developer jokes, and undocumented features
A secret room containing the message "Created by Warren Robinett" — the first Easter egg in video game history.
Entering Up, Up, Down, Down, Left, Right, Left, Right, B, A at the title screen grants the player a full set of power-ups — the origin of the most famous cheat code in gaming history.
Entering ABACABB on the Code of Honor screen re-enables all blood and fatalities that were censored from the Genesis port by default.
A hidden debug mode that lets the player fly freely through levels, spawn any in-game object, and view the game's internal ring counter and position data.
A glitched level accessible through a specific wall-clipping trick that sends the player to a corrupted "World -1," an infinite underwater loop that cannot be completed.
Two hidden levels rebuild stages from id Software's earlier Wolfenstein 3D, and the second ends with four corpses of Commander Keen — the hero of id's pre-Doom platformer — strung up on ropes that must be shot to finish the map.
A hidden cheat that replaces all bullet-impact blood splatter with large colourful paint blobs, giving the game a slapstick visual aesthetic wildly at odds with its spy-thriller tone.
The final boss of Doom II, the Icon of Sin, hides the digitised, impaled head of id Software co-founder John Romero behind its wall — and the only way to win is to shoot it.
A button sequence entered while the Capcom logo flashes on boot turns the screen blue and unlocks hidden match options the standard game keeps locked, including same-character battles.
A hidden world buried beneath Crocodile Isle, gated behind a Kremling toll-keeper who demands 75 collectible Kremkoins earned only by clearing the game's hidden bonus rooms.
A deliberately cursed in-game painting of a sad clown that, when hung in a Sim's home, causes the household's mood to deteriorate and summons a manifestation of the clown himself.
By equipping the W-Item materia and cancelling out of the second item selection during battle, the game duplicates the first selected item — allowing infinite copies of rare consumables like Megalixirs.
A password that starts the player near the end of the game with most power-ups collected, and crucially, displays Samus Aran as a woman in a swimsuit rather than in her Power Suit — one of the first times a major game protagonist was revealed to be female.
EarthBound contains hidden code that detects pirated copies of the game and punishes players with escalating difficulty before deleting all save data at the final boss.
NBA Jam contains secret playable characters including Bill Clinton, Al Gore, Prince Charles, and various Midway staff members, unlocked through specific initials and button combinations at the player entry screen.
The boss Psycho Mantis breaks the fourth wall by "reading" the player's memory card and making the controller move on its own — and the only way to beat him is to physically unplug the controller and move it to the second port.
A hidden level full of bipedal, club-wielding cows — created by Blizzard as a direct answer to a persistent fan rumour from the first Diablo that a secret cow level existed. The joke became one of gaming's most famous easter eggs.
One of Wolfenstein 3D's hidden levels recreates a Pac-Man maze in first-person 3D, complete with the original ghosts patrolling the corridors — a homage tucked inside the game that helped define the first-person shooter.
A reward for 100% completion: Yoshi waits on the roof of Peach’s Castle with a message from the development team, 100 extra lives, and a super-powered triple jump.
A cancelled cross-cartridge feature that hid mysterious eggs and an Ice Key in Banjo-Kazooie, intended to unlock secrets in the sequel Banjo-Tooie.
A grimly comic optional interaction where a character can microwave the resident hamster, with lethal consequences if you then show the remains to its owner.
A fourth-wall puzzle whose only solution — a radio frequency — is printed on the back of the game’s physical packaging, not anywhere in the game itself.
A hidden "Dream Team" room reached through one of the game’s multiple endings, where the creators appear disguised as monsters and speak to the player directly.
A sign hidden atop the game’s Golden Gate Bridge stand-in that reads "There are no Easter Eggs up here. Go away." — which, of course, makes it an Easter egg.