Country Switch

Video games are often released in different versions in different territories. The obvious way to do this is to program a different version of the game for each territory. But there's also a shortcut: release the exact same game in different locations, and program it so that the game does different things depending on what system it's played on.

This can produce odd results to anyone who has an imported game system; playing a domestic game on an imported system may cause it to behave like an imported game. For instance, if your system is Japanese, playing a domestic game may cause it to produce Japanese text.

This can also be used for Region Coding, where the "different thing" done on the wrong system is "not run".

A related phenomenon is that in some European releases with multilanguage support, the system's language settings will effect which language the game is played in; even in cases where language is not selectable per se, the media would have all languages. So if a, say, French or Spanish gamer bought a game from the UK, the game would play in their language even if there's no mention in the instruction manual or the packaging that the disc contains any language other than English. This is less prevalent in later games as the disc space becomes more of an issue.

In some cases (not, unfortunately, the PS3), it's possible to modify a game system with a switch (or even in some cases a converter) that lets the user select whether the system is domestic or imported. The user can then buy one game locally and make it play as either a domestic or import version by flicking the switch. This first became widely known during the Sega Genesis era. A decent Emulator will let the user pick what country the emulated system pretends to be.

MSX

 * G Gofer no Yabou Episode II becomes Nemesis 3: The Eve of Destruction
 * Akumajō Dracula becomes Vampire Killer.

Sega Master System

 * Aztec Adventure becomes Nazca '88.
 * Power Strike becomes Aleste.
 * Super Wonder Boy: Monster World, the Japanese version of Wonder Boy in Monster Land, plays in English on a western SMS—with a slightly different translation from the Western release, no less. Even the title is slightly different (instead of Wonder Boy in Monster Land, it becomes Super Wonder Boy: Monster Land).
 * Playing Wonder Boy III the Dragons Trap on a Japanese console will change the game's title to Monster World II and will enable FM sounds if an FM Sound Unit is installed. The text will still be in English though.

Game Gear

 * GG Aleste II becomes Power Strike II.

Sega Genesis/Mega Drive
See this link.
 * A lot of games have very minor changes in behavior from setting the country between Japan/US. Some only add/remove the "TM" on the "SEGA (TM)" screen before the actual game, or just change the title.
 * Fatal Labyrinth becomes Labyrinth of Death with kanji in the title, and plays in Japanese.
 * Streets of Rage changes to its Japanese name Bare Knuckle, among other changes. The sequel also becomes Bare Knuckle 2, but only if you change the country setting in the middle of the game.
 * Averted with Streets of Rage 3, since each version is coded to work only on its specific region.
 * Truxton becomes Tatsujin.
 * Mystic Defender may be one of the most extreme cases. This is really a Peacock King adaptation. Running it in Japanese mode changes the name of the main character to Kujaku, gives him a robe, makes fetus-like enemies flesh colored instead of green, gives the levels names, changes the effect of some of the magic, and uses a picture with the opening text, never seen if the game is played normally.
 * Even some Fan Translations take advantage of this. Fan translations for King Colossus and Battle Mania 2 are in Japanese or English depending on what kind of machine you are running them on.
 * Dashin' Desperadoes, when played on a Japanese Mega Drive, changes the game's title Rumble Kids. The curious thing about this is that Rumble Kids was never actually released in Japan.

Neo Geo and Neo-Geo CD
Just about everything for these systems uses the same ROM or disk in Japan and America. Neo-Geo games were notorious for censorship (particularly of red blood, as in Samurai Shodown) that could be avoided by switching your system to the Japanese version.

Atari Jaguar
Yes, even Atari's last gasp system did this. The game Sensible Soccer had fake player names when played on an American system and real ones on a European system, because of licensing restrictions.

Play Station 3
The Playstation 3 brought this feature to the modern era (the PS1 and PS2 couldn't run imported games at all without a Mod Chip, so there was never a chance for it to happen there). There's no known way to make a switch, but games will play differently on a Japanese and an American machine. Since the Genesis era, Japanese censorship has gotten stricter while American censorship has gotten looser, so now the American version may be the less censored one.
 * Uncharted notoriously is censored in Japan to not show blood. Early adopters of the PS3 sometimes bought Japanese systems; if they bought the American version of the game it would run as the censored Japanese version. Some reports claim that a patch changed this.
 * Resistance had this problem too, but it could be worked around by using a US save file.
 * Playing the Japanese version of Super Street Fighter IV on a western console causes the game to swap M. Bison's, Balrog's and Vega's name to match the western releases of the game. No doubt that if a western version of the game is played on a Japanese console, the reverse will happen.

Game Cube

 * Switching to the Japanese language option on Super Smash Bros Melee is a neat trip into localization. It even reveals the origin of the Motion Sensor Bomb item if you can read the text on its trophy entry (which in English is only given as "TOP SECRET").

Nintendo DS
This system is region-free, but can do something similar by checking the menu language. Of course, no switch needs to be installed in order to change the menu language and see the other country's version. (Unfortunately, this doesn't extend to the DSi, which doesn't let you change the menu language.)


 * Due to Capcom's unusual release schedule of the second and third Ace Attorney games, many imported them from Japan. If the Nintendo DS was set to English, the import games would display their titles in English on the main menu. If the DS was Japanese, so were the titles.
 * But the language of the (imported) game itself was still selectable at the start.
 * Sonic Rush and Rush Adventure both have English text if the language is English, the voice acting varies from the Japan and the rest of the versions.
 * All versions of Metal Slug 7 are identical and contain Japanese, English and all European languages, yet somehow it took them 4 months to release the first non-Japanese version.
 * Playing Konami's Collectors Series: Arcade Hits on a console set to Japanese will change the menus and text to Japanese. It will also change the version of Gradius included in the compilation from the "USA" version (which is actually the Nemesis variant with the logo on the title screen changed back to the Gradius one) to the Japanese original (which has some difficulty differences compared to Nemesis). The Contra logo also changes to the Japanese one. Strangely, all the other games which had different names between regions (such as Rush N Attack and Rainbow Bell) remain unchanged.

PC
Some PC games make a point of installing or running different versions of the same game based on your computer's locale setting.
 * Spore changed its language according to your computer's locale settings, as do many other EA games. This could be reversed by copying the desired language files over the language the game chose.
 * The open-source game The Battle for Wesnoth does this too, but it can be overridden by starting it as wesnoth --dummy-locales (which makes all languages available).
 * Some applications weren't coded with the different locale settings in mind. Using them with the "wrong" locale can give results that range from text not fitting on the screen to crashing at launch. Or in particularly bad cases, corrupting data.
 * Tools such as Applocale help, a bit.

DVD
It is a little-known fact that DVDs can do this. This is separate from normal DVD Region Coding; DVDs can be programmed to play different content depending on what region the player is from.
 * The Bubblegum Crisis Tokyo 2040 DVDs were released in Japan identical to the American ones, but are programmed not to show any trailers on a Japanese player.
 * Of course, people figured out that you can use this to add another layer of Region Coding protection.

Blu-Ray
Blu-Rays can use the menu language for similar effects within the same region. Note that Japan and the USA are in the same region. The changes need not have anything to do with menus.
 * Setting the menu language to Japanese on Batman Begins and Batman Gotham Knight magically adds a Japanese track, removes most other languages, and forces subtitles in some places. If the menu language is English, the Japanese track is completely invisible and can't be seen or selected in any way.

PlayStation 2

 * If you're using a Japanese PS2, and have the system language set to Japanese, the Japanese version of Rez will run in Japanese. But set the system language to English, and you're in for a surprise: the game's text will be in English!
 * Likewise, with the Japanese version of Sonic Gems Collection, if the system language is set to Japanese, the logo and menus will be in Japanese and Sonic CD will play the original soundtrack. Change the system language to English, and the logo/menu text changes with it... and Sonic CD plays the North American soundtrack.

Sega Saturn

 * Switches existed for this system, but this always affected region lockout—a game could never run in two regions, so couldn't have different behavior depending on region. However, the Japanese game Soukyugurentai had a glitchy, partial, language change which took effect if you set the country to US and used a Game Genie to prevent this from causing the region lockout that it normally does.

Sega Dreamcast

 * If you play De La Jet Set Radio, a special version only released in Japan (and even then only through the Sega Direct service), on a Dreamcast with its System language set to English, all the In-game text becomes English. The same is true for Spanish, Italian and German, though all in-game voices remain in what ever language they where originally.