West Side Island is an island that Sonic the Hedgehog visits after saving South Island from Dr. Robotnik and where he first meets Miles "Tails" Prower. It is the main setting of Sonic the Hedgehog 2. Many zones of the island make reappearances in later games, even if West Side Island itself is not mentioned.
Sonic the Hedgehog 2
Sonic the Hedgehog was looking for new adventures following the events of the previous game when he discovered West Side Island. Sonic landed his personal plane, the Tornado, on the island to check it out and relax, not paying attention to the fact that a certain metallic flying object was chasing him and suspiciously landed on the other side of the island.
It is said that a very long time ago, the people of West Side Island used a mysterious stone to advance their civilization and achieve prosperity. However, when those people tried to use the stone for the wrong reasons, their prosperity vanished overnight. It is believed that the kami sealed away the stone within the island's depths.
One day shortly afterward, Sonic noticed a shy orange fox tagging behind him, who nervously scurried back into the welcoming shade of the still palm trees when he was spotted. When Sonic was not looking, the peculiar fox barely managed to keep up with the blue hero. The fox's name was Miles Prower, though he was known as "Tails" due to his two special tails, which often made him the target of bullying. However, something changed in Tails when he saw Sonic come to the island, and he made up his mind that he wanted to be cool like Sonic. Realizing that the young kid was harmless, Sonic made friends with him and allowed him to hang around as he freely explored the island.
On an early afternoon, Tails discovered a lone aircraft stranded at the beach. Being a budding fan of machinery and vehicles, he rushed to take a closer inspection. He was admiring its magnificent build until he noticed that Sonic was taking a nap under its wing. Realizing that Sonic owned the plane, Tails gently retreated to the other side of it so as not to wake him. Suddenly, an ominous flash occurred in the direction of the nearby forest, followed by a terrific explosion. The wild fire blew away various debris, which Tails avoided by taking cover underneath the Tornado as he witnessed robots violently excavating the area. This ceaseless activity threatened to blanket the entire island in its destructive flames.
It turned out that Dr. Robotnik detected the presence of all Chaos Emeralds after following Sonic, including the lost seventh one spoken of in the island's legend. He took the opportunity to kidnap the island's animals to rebuild his Badnik forces and finish his ultimate weapon, the Death Egg. Robotnik now ruled the factories, refineries and cities. He's grabbed control of everything — except the seven Chaos Emeralds. The speedy hedgehog went off into the forest to set things right and the curious fox followed.
Sonic and Tails journey through all zones of the game to chase down Robotnik. Eventually, Robotnik makes his retreat from the island. Sonic and Tails take to the skies of Sky Chase Zone as they pursue Robotnik's flying ship, Wing Fortress. The Tornado is shot down, taking its pilot with it. The player character (Sonic by default) takes on the fortress only to find Robotnik escaping again. However, his partner comes back with a hasty rocket engine repair. The player character jumps off the Tornado and onto Robotnik's escape vehicle, managing to enter the newly-created Death Egg Zone. He manages to defeat the final line of defense: Mecha Sonic and the Death Egg Robot. Just a moment later, the Death Egg explodes as the bright light could be seen above the West Side Island. The remaining pilot finds the player character with the Tornado in the middle of the sky and thus the island was freed.
- Emerald Hill Zone - A bumpy, tropical peninsula plain riddled with abandoned emerald mines.
- Chemical Plant Zone - A factory built to manufacture industrial chemicals (possibly to supply Metropolis).
- Aquatic Ruin Zone - The half-submerged ruins of an ancient city.
- Casino Night Zone - A casino full of jackpot machines and similar that supplies West Side island with tourism money.
- Hill Top Zone - A mountainous region of tall "block mountains" and lava-flooded caves.
- Mystic Cave Zone - An extensive system of crystal mines full of bridges, spikes and other obstacles.
- Hidden Palace Zone - A mysterious ruin located in the deepest recesses of the island. (2013 re-release only)
- Oil Ocean Zone - A massive valley flooded by the spillage from various oil rigs.
- Metropolis Zone - A huge, industrial city made entirely of pipes, mechanical contraptions, and huge factories. It was briefly used by Dr. Robotnik as a Badnik manufacturing plant.
And above the island:
- Sky Chase Zone, where flying Badniks patrol the island's airspace.
- Wing Fortress Zone, the Doctor's aerial fortress.
And even higher above:
- Death Egg Zone, Dr. Robotnik's own personal doomsday moonlet.
Sonic Drift 2
Many zones of West Side Island are seen as multiple race tracks in Sonic Drift 2, although once again the island itself is not mentioned at any form. Many of these included Emerald Hill Zone, Hill Top Zone, Casino Night Zone and Mystic Cave Zone. There are also some original tracks as well, that would take place of the island such as Balloon Panic, which would possibly taken place of Emerald Hill Zone.
Sonic the Fighters
After the first appearance, some of West Side Island's zones later appear as fighting arenas in Sonic the Fighters. One of them is Casino Night, where the player's opponent is Fang the Sniper. Also several other arenas looks like familiar to the other zones of Sonic the Hedgehog 2. For example, Dynamite Plant is mixed of Chemical Plant Zone and Oil Ocean Zone, as well Giant Wing bears resemble of Wing Fortress Zone.
At the intro demo of the game, it also seems that Tails's workshop might actually located on West Side Island.
Sonic Chronicles: The Dark Brotherhood
West Side Island (although not being mentioned by its name) might appear as one of the islands in Sonic Chronicles: The Dark Brotherhood, due to ruins of Metropolis being there. This also would confirm Blue Ridge Zone being as part of the island.
Appearances in Other Media
In the Archie Comics, Westside Island is a location on Mobius. Presumably, it did not initially exist on Mobius until after the Prime Zone's timeline and reality was rewritten by the Super Genesis Wave. It is the location of Mobotropolis, Knothole Village and the Wood Zone.