Unlockable games

The term unlockable games refers to full video games that can be unlocked within another videogame, often as easter eggs. Often these unlockable games are earlier entries of the series of the game in which they are hidden, such as NES "Ninja Gaiden" series in the Xbox version of "Ninja Gaiden", which become available after beating the game with certain requirements.

Examples

*In "", you can unlock the original "Pitfall" game.
*In Tekken 5 you can play the first Tekken to Tekken 3.
*In the PC game "Day of the Tentacle" by LucasArts you could play "Maniac Mansion", the predecessor to Day of the Tentacle.
*In NHL 06 NHL 94 is included in the PS2 version.
*"Animal Crossing" features nineteen unlockable NES games.
*In "Donkey Kong 64", the games "Jetpac" and the original "Donkey Kong" can be unlocked in Kranky Kong's lab and Frantic Factory respectively.
*In ', the arcade versions of "Star Wars" and ' can be unlocked by meeting certain requirements.
*' features the "TMNT" arcade and ' features "".
*"Metroid" was an unlockable in two different games: by finishing "Metroid Fusion" and connecting it to "Metroid Prime" with the Nintendo GameCube Game Boy Advance Cable; in "" it becomes available after beating the game.
* In "House of the Dead III" for Xbox, "House of the Dead 2" can be unlocked after you beat the game.
* In "", players can unlock "the original Prince of Persia". "Prince of Persia 2" is also unlockable, but only on the Xbox release.
* In "", players can unlock 12 Sega Game Gear games: Sonic the Hedgehog, "Sonic Drift", "Sonic Chaos", "Sonic Spinball", "Sonic Labyrinth", "Sonic the Hedgehog 2", "Dr. Robotnik's Mean Bean Machine", "Sonic Triple Trouble", "Sonic Drift 2", "Tails' Skypatrol", "Sonic Blast" and "Tails Adventure".
* In "Pac-Man World 2", Players can Unlock 4 classic Pacman games in the arcade by collecting a certain amount of tokens. The games are "Pac-Man", "Ms. Pac-Man", "Pac-Attack", and "Pac-Mania".
* In "Return to Castle Wolfenstein", "the original Wolfenstein 3D" is unlocked after the player completes the game.
* In the Saturn release of "Duke Nukem 3D", "Death Tank Zwei" can be unlocked either by shooting out every toilet in the game, or by having a save file from another game by Lobotomy Software on your memory unit.
* In "Project Gotham Racing 2", "Geometry Wars" is unlocked by entering the garage, entering walk mode, walking to an arcade machine, and pressing A.
* In "", "Snake's Nightmare" is unlockable by saving and loading your game while in the prison cell. While this is not a full fledged game, it is reminiscent of many other video games.
* In Sonic Mega Collection, players can unlock 5 more games by playing games a certain number of times (7 in the Japanese version including The Ooze and Comix Zone): 3 lock on games, including Blue Sphere, Knuckles in Sonic 2, Knuckles in Sonic the Hedgehog 3 and 2 Sega Genesis classics (Ristar and Flicky)
* "Super Smash Bros. Brawl" has a feature called Masterpieces that allows the player to play demos of the characters Games of Origin. For example, you can play Super Metroid (one of Samus Aran's Games from the Metroid series), but the demo has a strict time limit after which the game resets and returns to "Brawl". The demos can be started over and played as much as the player wants but will still have the same time limit.
* In "", versions of "Centipede" and "Missile Command" can be unlocked by finding their arcade machines in the game's levels.
* In several Grand Theft Auto games, there are arcade machines where you can play games.
* In "Ninja Gaiden (Xbox)", you can unlock the first 3 "Ninja Gaiden" games for the "Nintendo Entertaiment System".
*In Mortal Kombat Shaolin Monks , You can unlock Mortal Kombat 2 ( Arecade Ver. ) by completing Smoke's 5 Missions in the story mode , Or Hold L2 and input SQUARE, UP, DOWN, RIGHT, LEFT, R2, SQUARE. Release L2 in the main menu.