— Sonic the Hedgehog, "Robotnik's Revenge"
Sonic the Hedgehog is the main protagonist of the anime series, Sonic X. Lightning fast on his feet, but super slow to lose his cool, Sonic is always revved up and ready for a run-in with his archenemy, Dr. Eggman. Sonic's fear of water is even more present in the series than in the videogames.
Sonic hails from an unnamed world in a parallel dimension to Earth. His back-story is a mystery but it's known that he befriended Tails, Knuckles, Amy, Cream and Cheese and many small animals as well as battling Eggman. One day, he attempted to rescue his friends Cream the Rabbit and her Chao friend Cheese from Dr. Eggman as well as foil the doctor's latest plot to control the world with the power of the seven Chaos Emeralds. Unfortunately, an accident initiated Chaos Control, which transported Sonic, Eggman, all of Sonic's friends and all within a ten mile radius to Earth. On Earth, Sonic befriended Chris Thorndyke, who rescued him from drowning in a swimming pool and then allowed Sonic,Tails, Amy, Cream and Cheese to stay hidden with him in his house. He also forged a friendly rivalry with Chris' second uncleSam Speed, a cop who chases criminals in a racecar. He is initially hidden in Chris' home and boggles the human race with his being, people think he's an alien or machine. While Sonic was mostly covert, Eggman made himself known as he tried to conquer the new world. Sonic eventually destroys Eggman's first base and is hailed as a hero along with all of his friends. Sonic destroys Eggman's second base by becoming Super Sonic by finally gathering all the Chaos Emeralds after Chris dropped them into the ocean, causing Chaos Control to bring some aspects of his world, like Angel Island, to Earth.
After the adaptations of Sonic Adventure, Sonic Adventure 2, Sonic Heroes and Sonic Battle, it was discovered that Sonic's world and Earth were merging (possibly due to Sonic bringing parts of his world to Earth) which would lead to the stopping of time. The only way to save both planets was to return Sonic and his friends home. After everyone but Sonic had went through, Chris took him away, eventually to his parents old summer home. Chris tells Sonic how much he will miss him and how much of a friend the hedgehog was. Sonic gathers the Chaos Emeralds and after taking Chris for one final run, returns to his home universe.
Upon returning, Super Sonic easily destroys Eggman's latest battleship, saves Tails and then meets Amy, giving her a rose and telling her that he loves her (Japanese and French versions only).
Six months later, Super Sonic battles Dark Oak in outer space. He spreads the Chaos Emeralds throughout space and falls back to the planet. He is found and nursed to health by Dr. Eggman. Later the heroes gather the Chaos Emeralds in a space journey very loosely based on Sonic Heroes and Shadow the Hedgehog. In the end Super Sonic and Super Shadow destroy Dark Oak and they all return home. Sonic watches as Chris is flown away back to Earth and declares war on Eggman for making Chris leave so soon. He says "I'll never forgive you, Eggman!" ("Life never stays slow around here for long, thank goodness! Watch out, Eggman, I'm comin' at ya full speed ahead!" in the English version). In this season, Sonic seems to care about Amy a lot more than in Seasons 1 and 2.
Sonic is a habitual daredevil who is honest, loyal to friends, keeps his promises, and dislikes tears. He took the young Tails under his wing like a little brother. Even though he isn't intrigued by the marital proposals from Amy Rose, he seems to share her feelings to the point of telling her that he loves her in the Japanese and French versions of episode 52. With Knuckles, he shares a friendly rivalry (similar to the game one), but the two can be great teammates, though Sonic simply can't resist teasing him whenever he has the chance to. Even though he meets Chris at the beginning of the series, he quickly becomes his friend and treats him like a younger brother similar to Tails. He is mostly seen napping, watching television or running.
In times of crisis, he focuses intensely on the challenge as if his personality had undergone an astonishing change. Sonic's greatest strength is his running speed, which is faster than the speed of sound. He appears as a blue blur when he runs. He can use the Spin Attack like in the games and appears in 3D, in this state he can break through virtually anything and a ring can increase his power similar to SatAM.
When seven Chaos Emeralds are collected, he is able to transform into Super Sonic, a faster, stronger and invulnerable version of himself that can fly, teleport and move faster than the speed of light. He can also heal people with a touch. He has used the Super Sonic form against Perfect Chaos, Biolizard, Eggman, Dark Oak, and Super Shadow.
- Miles "Tails" Prower (Best friend; like brothers)
- Knuckles the Echidna (Friendly Rival)
- Amy Rose (Self-proclaimed girlfriend; returns her feelings to an extent)
- Rouge the Bat
- Shadow the Hedgehog (Arch Rival)
- Cream the Rabbit (Good Friend)
- Christopher Thorndyke (Best friend)
- Chuck Thorndyke
- Vector the Crocodile
- Espio the Chameleon
- Charmy Bee
- Vanilla the Rabbit
- Big the Cat
- Tikal the Echidna
- Cosmo the Seedrian
- Dr. Eggman (ally against the Metarex)
- "Kids, don't use formula one race cars to chase hedgehogs!" - While on a Speed Team car in "Chaos Control Freaks."
- "Oh! What a great view!" - After running up a tree in the Japanese version of "Cracking Knuckles" in English.
- "So, are you up for a race, eh?" - After he thought that the cheetah would race against him in "The Dam Scam".
- "Good job! Our captain!" - To comfort Tails when he thought he wasn't a good captain.
- "Don't you worry Amy, I never will!" - Sonic telling Amy that he would never leave her again in "A New Start".
- "If I don't get to the city fast, there won't be anything left to save!" - Sonic realizing that Chaos is going on a destructive rampage.
- "YOU CAN'T STOP ME!" - Sonic during his fight with the gargantuan dragon, Chaos, after the beast spat a beam of fire.
- "Is that the best you can do?" - Sonic just moments before he dives into Chaos's huge jaws.
- "I'd like to, but I don't get involved in fights I can't win. You're on your own." - When Knuckles asks Sonic for help when the girls (Amy, Cream, and Cosmo) start "knocking some sense" into Knuckles in episode 54.
- "Life never stays slow around here for long! Thank goodness! Watch out Eggman, I'm coming at you full speed ahead!" - In the dub version of the final episode when he declares war on Eggman.
- "I'm just a guy with a need for speed! They call me Sonic the Hedgehog!" - Sonic while chasing Shadow on the ARK.
- "Your brain must be slower than your feet!" Sonic when taunting Knuckles in Cracking Knuckles
- "Yea, I have a name. My name is Sonic the Hedgehog" Sonic meeting Chris for the first time.
- Sometimes, when Sonic runs, his feet move in a circular motion. This could be a reference to the 2-D games as his feet would move in a similar fashion at full speed, as well as the other three shows which appeared earlier.
- Sonic also seems to have some kind of super strength, as seen when he was able to push back the E-18 Guerra-Hard robot, which was over ten times his size. As well as being able to hold back a fish Metarex with very little or no effort with one hand. Also, in several episodes he's seen punching Eggman's robots.
- It has been said that Sonic never cries, yet in the second season finale, "A New Start," as Sonic is carrying Chris, you can see tears coming from his face and onto Chris', also in episode 52 when Amy is explaining her feelings to Sonic if you look you can just barely see a small teardrop forming in his right eye.
- In the Japanese version, Sonic uses the most Engrish dialogue out of all characters.
- No matter what angle you see Sonic (excluding when he is falling from outer space after his first fight with Dark Oak), he has three quills. As Super Sonic, he has five quills.
- Sonic is shown to enjoy taunting Eggman by turning around, sticking out his tongue, pulling on his eye socket and slapping his rear.
- Both Sonic and Chris appeared in the most episodes of Sonic X (76).
- In the episode "Skirmish in the Sky," Sonic's arms are mistakenly colored blue when he holds on to the Egg Fort.