prologue: Once Upon a Planet... is a Sonic's World complete story that first appeared in Issue 25 of Sonic the Comic. The adventure was almost unique for being a series of flashbacks as told by the Kintobor Computer who described the world of Mobius. It was also the first Sonic's World strip and directly linked to Part 1: Kintobor spelled backwards is....
The galaxy containing Mobius is 117,63222 light years from Planet Earth, existing in a parallel dimension and in a different time zone, with the whole region consisting of dark matter. If you could get there, you would have seen a beautiful, unspoilt world before Doctor Robotnik came along. The planet is made of several continents, which are divided into different Zones (too many to mention). South Island is home to the Hill Zones, namely the Green Hill Zone and the Emerald Hill Zone. The latter is home to hero Sonic the Hedgehog, who lives in a secret underground laboratory.
Elsewhere, Robotnik lives in the Special Zone, commanding his forces from the Egg Fortress (shown by a Moto Bug force flying to the Starlight Zone). Other Zones are partly run by his minions, such as the Casino Night Zone once ruled by the Marxio Brothers. Orbiting the world is the Miracle Planet, a beautiful, uninhabited place that only appears over Mobius once a month. Nobody knows where it goes. Robotnik is after the six Time Stones, which he could use to control time and become unstoppable.
Robotnik controls Mobius and the world is choking under his influence. He no longer has the Chaos Emeralds so is no longer unstoppable, yet he still rules. Most Mobians believe that Sonic will take care of Robotnik's empire for good one day. And, if you're wondering about the humble narrator who knows all the secrets of Mobius, it's the Kintobor Computer!
- The title of the story is the first to begin with a non-capital letter and to contain an elipsis.
- The definition of Mobius' location seems to have changed over time, since there is no mention of being surrounded by dark matter any more. Amy Rose and Tekno the Canary were also on their way back to Mobius by spaceship in Earthbound, although they may have been lost in another dimension.
- Mobius is also shown to look significantly different in the future. Worlds Collide show it to look much more like Earth, rather than a bright ball of white.
- No further mention of continents have ever been made. The closest reference is in the Control Zone which mentions Adabat, one of the regions on Sonic Unleashed.
- One of the stalls in the Emerald Hill Zone sells "apples 'n' pears". This is cockney rhyming slang for stairs.
- Similarly, the next stall seems to be selling bananas, but Porker Lewis is also selling these across the road.
- The Egg Fortress looks completely different to its past and future appearances.
- The Starlight Zone gets its first mention, although it won't appear until next issue.
- It is revealed that the Marxios still work at the Casino Night Zone, overseeing its reconstruction, referencing the adventure in Casino Night.
- Miracle Planet is referred to as the "Little Planet", the name given in the games.
- Six Time Stones are shown, although Sonic the Hedgehog CD shows there to be seven. The Sonic Terminator, currently running alongside this story and written by the same writer, has only one Time Stone and looks drastically different.
- The image of Robotnik holding the planet is repeated for real in Show of Strength.
- Robotnik is said to no longer hold the Chaos Emeralds, even though he has never been seen to hold them in the comic or games.
- The Chaos Emeralds are shown to be all green, rather than their individual colours. They are also shaped wrongly.