History Fridge / SonicTheHedgehogCD

* There is a reason for Eggman's robots in this game are all bugs. Unlike in previous games, where the good doctor had avian, reptilian, amphibious, and mammalian Badniks, as the game deals with time travel, having a monkey Badnik in the age of the dinosaurs would cause some cases of FishOutOfTemporalWater. Bugs meanwhile were around before most chordate animals and are still alive today.
** Further Brilliance: Why are the Badniks in CD using living cores that sprout into flowers when shattered? Simple: Plant seeds can remain bioelectrically viable for far longer than animals, so Eggman used flower seeds as the bioelectrical cores of any badniks he would be deploying for the extended time periods from Past to Future. They're also easier to harvest than animals, even if the resulting badniks turn out less powerful/intelligent than the traditional animal-powered ones he can field many more of them at once, ''and'' store them for long-term deployments without needing to constantly replace the 'cores' of the badniks due to the small animals dying from old age.

** A similar design oversight happens with the Quartz Quadrant boss, where it would normally be a rather foolproof plan: trap Sonic in a room he can't run out of with a conveyor belt, drop spread bombs on him and lock the exit with spikes and his wall. The big problem? He put his own controls inside the wall, and it's actually touching the ground. That conveyor isn't just running passively like the rest, it actually only moves when Sonic is running on it -- Eggman ''underestimated'' how fast Sonic could actually push the conveyor and it grinds his wall up.
* Why do the Past versions of zones have the same music in both the Japanese soundtrack and the American soundtrack? Because you can change the present and the future but you can't change the past.

* Why is Sonic's Spin Dash is animated differently from the other games? He was just starting to develop the move. Also while the Super Peel-Out technique may look cool and increases your speed, it was mostly impractical as there was a good chance of colliding into your enemies without any means of offense other than rolling.
* It seems odd that the third Zone in every Round is what instantly forms the Good/Bad Future as soon as you arrive, whereas the previous two Zones all start in the Present. Especially with how, in the first few Rounds, there's little to no sign of any tech. However, this is a good indicator of Eggman's influence in the past having gradually more devastating consequences in the future if Sonic doesn't intervene - in Palmtree Panic, he's already gotten a head start, however little, just to test the waters and see what he can get away with. By the time of Metallic Madness, he's already in the process of constructing his final base with little sign of what used to be there before he arrived. Sonic's actions end up being the deciding factor in whether Eggman achieves what he desires, or is stopped before the ball gets rolling.
** There's also a reason why getting all the Time Stones guarantees Good Futures from then on, even if you missed all the robot generators beforehand. Sonic can use the stones to make it so that Eggman's efforts are immediately undone, without needing to personally intervene. He still needs to deal with the man in the future, of course, but with the Time Stones, he doesn't need to go out of his way to ensure Little Planet's prosperity - he just has to catch up to his nemesis.
*** Alternatively, Eggman hasn't already collected the Time Stones yet in the Present, but will do so in the Future - meaning collecting them now prevents Eggman from ever getting his hands on them, which ensures he can't then use them to MakeWrongWhatOnceWentRight and preventing the teleporters from existing in the first place - Hence why collecting them all is an [[InstantWinCondition Instant Good Ending Condition]], even if you never once travel to the Past.

*** Alternatively, Eggman hasn't already collected the Time Stones yet in the Present, but will do so in the Future - meaning collecting them now prevents Eggman from ever getting his hands on them, which ensures he can't then use them to SetWrongWhatOnceWentRight and preventing the teleporters from existing in the first place - Hence why collecting them all is an [[InstantWinCondition Instant Good Ending Condition]], even if you never once travel to the Past.

* There is a reason for Eggman's robots in this game are all bugs. Unlike in previous games, where the good doctor had avian, reptilian, amphibious, and mammalian Badniks, as the game deals with time travel, having a monkey Badnik in the age of the dinosaurs would cause some cases of FishOutOfTemporalWater. Bugs meanwhile were before most chordate animals and are still alive today.

** Which explains why enemies like the Kama-Kama was laughably weak compared to its DemonicSpiders successor, the Slicer from ''2''.

** Which explains why enemies like the Kama-Kama was laughably weak compared to its DemonicSpiders successor, the Slicder from ''2''.

* Why is Sonic's Spin Dash is animated differently from other games? He was just starting to develop the move. Also while the Super Peel-Out technique may look cool and increases your speed, it was mostly impractical as there was a good chance of colliding into your enemies without any means of offense other than rolling.

* Why is Sonic's Spin Dash is animated differently from other games? He was just starting to develop the move. Also while the Peel-Out Dash may look cool and increase your speed, it was mostly impractical as there was a good chance of colliding into your enemies without any means of offense other than rolling.

* Why is Sonic's Spin Dash is animated differently from other games? He was just starting to develop the move. Also while the Peel-Out Dash may look cool and increase your speed, it was mostly impractical as there was a good chance of colliding into your enemies without any means of offense.

* While the method by which Sonic activates time travel (running really fast) is likely due to SuperSpeed being his signature power, it also evokes [[Franchise/BackToTheFuture another franchise in which moving a certain speed is required to travel through time]]. This is {{Lampshaded}} in the Steam remake where the achievement for time traveling for the first time is called "88 miles per hour".

* The Bad Futures, [[NightmareFuel horrifying as they are already]], become even worse when you realize that the scale of Eggman's plan means that he is rendering ''an entire planet uninhabitable''.

** Palmtree Panic's tropical feel: In Japan, the closest to the tropics that Japan can get is Okinawa, which explains why in America the music now sounds like it's from the Caribbean.
** Collision Chaos: Both have an urban feel to them but implemented differently. Japan does it like it's Akihabara, while America does it like it's either Chicago or New York.
** Tidal Tempest's watery feel to it is implemented a bit differently in both soundtracks. In Japan it has the ocean waves and an ancient feel to it while America uses the ancient feel for the Bad Future, but it still has the watery feel to it with the slap bass sounding like drops of water.
** Quartz Quadrant has a sort of rocky feel to it. This is apparent in the Japanese version, while America took rock as rock and roll.
** Wacky Workbench has an industrial feel. In Japan, this is heavily reflected in the bad future with the warning siren going off, while America has it sound like a building is being put up.
** Stardust Speedway is a bit interesting as Japan does it like a bright night on the road, while America has it sound like Sonic is on a racetrack, and adds a bit of foreshadowing to his eventual race with Metal Sonic.
** Metal Madness both involve a techno/rock feel to them. In Japan, it includes the late Casey Rankin chewing out Eggman in rap form that all of his plans have failed and his ultimate weapon has fallen. America meanwhile is heavy on the techno in the Present and Good Future, while heavy on the rock in the Bad Future, showing that Eggman is starting to descend into insanity.

* Why do the Past versions of zones have the same music in both the JP soundtrack and the US soundtrack? Because you can change the present and the future but you can't change the past.

** This should be taken with a grain of salt, as obviously this is non-canon, and was likely done for humour. Out of spite and boredom, Sonic got tired of waiting for the player to move him.

** This should be taken with a grain of salt, as obviously this is non-canon, and was likely done for humour.

** Although obviously this is non-canon, and was likely done for humour, so it should be taken with a grain of salt.

** Tidal Tempest's watery feel to it is implemented a bit differently in both regions. In Japan it has the ocean waves and a ancient feel to it while America uses the ancient feel for the Bad Future, but it still has the watery feel to it with the slap bass sounding like drops of water.

* Each boss, with the possible exceptions of Palmtree Panic and Metallic Madness, [[{{Antepiece}} use the zone's gimmick]]: Collision Chaos has many pinball flippers lying about and the boss is a giant pinball table, Tidal Tempest's second phase takes place entirely underwater, Quartz Quadrant's has conveyor belts all over and the boss zone features one that functions as a treadmill, Wacky Workbench uses the electric floors to bounce the debris up to Eggman and Stardust Speedway is the most speed-oriented zone in the game; Naturally, it's fight is a race against Metal Sonic.