Sonic the Hedgehog O is Star Crash Inc.'s classic style Sonic the Hedgehog game. It contains elements from Sonic the Hedgehog 1, 2, 3, & Knuckles, Spinball, and Adventure. It is considered an "alternate universe" from the main series.


The game loosely follows the plot of Sonic the Hedgehog 1, 2, 3, and & Knuckles. At the end of each game's plot points, Dr. Eggman escapes to another island, eventually messing with Knuckles and making him an enemy of Sonic. After defeating Knuckles twice and driving Eggman towards his lair, Knuckles helps him. (Amy has also been helping Sonic.) Eventually, they (along with Rouge and Mighty who they have befriended) encounter Eggman at his Death Egg. They find out he has built the giant Egg Emperor, and infused it with a helpless and supercharged Chaos. After defeating the Egg Emperor suit, it crashes into the lab holding Eggman's super-realistic hedgehog android, Shadow. Shadow's wires latch onto the Emperor Suit and power it up. Even Eggman has to help a little to stop it from destroying his labs. Afterwards, Sonic goes home and Eggman reforms. However, upon collecting all seven Chaos Emeralds, the Chao Graveyard is revealed where the supercharged Chaos has been lurking. Being fused with the Emperor Suit has mad it go insane. Upon defeating it, peace is truly restored. At the end of the secret credits unlocked from beating him, you see the Shadow android wake up to see a bright light...


The gameplay is similar to that of the classic Sonic games, showing your character from the side. No homing attacks or similar actions are present. The only playable character is Sonic on the first run through. After you beat a level, you can play as any of your partners you encounter throughout the game in that level (Tails, Amy, Knuckles, Rouge, or Mighty.) Each one has their own skills. Partners, when you are not playing as them, follow you around. In 2-player mode, the second player can play as your current partner or after you beat the level any one of your unlocked partners. During the Robot Death Zone (in which all of your partners are present) they can choose who to be even before you beat the level. The graphics are new like in Sonic the Hedgehog 4, Sonic Colors, and Sonic Generations. However, there are not many distracting visuals in the backgrounds.


South Island

Main Isle

Echidna Isle

Floating Island

Tall Tower

Death Egg

Special Ruins


  • The name refers to the fact that the game is a full circle, containing story and characters from later on in the series without going overboard and playing through the stories from the original plot to a modified Adventure.
  • The game's story is an alternate universe from the main Sonic series.
    • An example of this is the fact that Shadow in this game is an android.