The series follows a group of anthropomorphic animals that accidentally teleport from their home planet to Earth after attempting to save one of their friends from their enemy Doctor Eggman.

Separated, Sonic the Hedgehog is saved by a human boy named Chris Thorndyke, who helps him find his friends while repeatedly scuffling with Doctor Eggman and his robots over control of the powerful Chaos Emeralds, and becoming celebrities.

The final story arc sees Sonic and his friends return with Chris to their world, where they enter outer space with a newfound plant-like creature named Cosmo and fight an army of aliens called the Metarex.

Sonic and his friends find themselves landing in the city of Station Square, where they befriend twelve-year-old Christopher "Chris" Thorndyke—a lonely young boy, whose parents, movie-star mother Lindsey, and corporate executive father Nelson, tend to be absent with work, leaving him to be looked after by his grandfather Chuck, maid and chef Ella, and butler Mr. Tanaka.

In the course of battling Eggman, Sonic and the others befriend Chris' friends Danny, Frances and Helen, while slowly becoming celebrities thanks to their exploits, eventually being accepted amongst the human population, despite reservations of what might happen when the seven Chaos Emeralds are found.

After Station Square is rebuilt following the attack by Chaos, and Sonic and Shadow prevent Space Colony ARK from crashing into Earth, another Chaos Control event brings several inhabitants of Sonic's world to the planet, including the Chaotix Detective Agency—Vector the Crocodile, Espio the Chameleon, and Charmy Bee—and Vanilla, Cream's mother.

Eggman launches further schemes following the ARK incident, even when briefly captured by the government, whilst Sonic and his friends provide shelter for a robot named Emerl, who later goes on the rampage after coming into possession of a Chaos Emerald and forcing Cream to stop it (the story arc being a loose adaption of Sonic Battle).

As a result, Sonic, Eggman, and the others are forced to return home to prevent this, with Chris having to bravely allow his new friends to go, but with hope of seeing them again.

Alongside the group, Eggman also pursues after the Emeralds, accompanied by Rouge, and aided by Shadow, whom he had recovered following his supposed demise.

4Kids removed alcohol consumption, coarse language, instances of breaking the fourth wall, and numerous sexual scenes.

[11] Unlike some other series that 4Kids translated around the early to mid 2000s, such as Kirby: Right Back at Ya!, Sonic X suffered no full episodes being cut.

Producer Michael Haigney personally disliked realistic violence in children's programs, but had not intended to make massive changes himself.

[13] 4Kids president Norman J. Grossfeld invited Jason Griffith and Mike Pollock to audition for Sonic and Eggman, having known them from their work on Ultimate Muscle and Kirby: Right Back at Ya!

[28][29] For the 60th anniversary of TMS Entertainment, the company streamed a select number of episodes on its YouTube channel, available with the original Japanese audio with English subtitles, from August 5–9 and 12–16, 2024.

[32] From 2003 to 2009 in the United States, 4Kids Home Video and their exclusive distributor FUNimation Entertainment released VHS tapes (until 2005) and DVDs of the series in single-release volumes and later multi-disc boxsets.

[34] Discotek Media released the 8-disc DVD set, "Sonic X Collection 1" in North America, which includes the English-dubbed seasons 1 and 2 (episodes 1–52) on November 22, 2016.

[40] 4Kids musicians John Angier, Craig Marks, Joel Douek, Louis Cortelezzi, Manny Corallo, Matt McGuire, and Ralph Schuckett, known for their work on the Yu-Gi-Oh!

[42][43] In October 2004, ShoPro licensed four manufacturers to create Sonic X merchandise, they variously produced items such as toys, bedding, beach towels, backpacks, stationery, and pajamas.

[63] Afterwards, he temporarily fires Decoe and Bocoe and creates replacements, Dukow and Bukow,[64] who kidnap Sonic and give him to an organization called S.O.N.I.C.X.

The game features three levels, each with its own math concepts: the city Station Square (sequencing, counting in increments); Angel Island, the home of the Master Emerald (addition), and Eggman's base (subtraction).

KidzWorld gave a positive review, praising its ease of learning, low cost, and inherent strategy, but also noting that it feels more like a generic card game with Sonic characters than like a wholly Sonic-based product.

Jones described Chris as "a dull, boring, uninspired character" and also described Tanaka and Ella as "bland" stereotypes of Japanese and African-Americans, respectively.

Jones also criticized the presence of Amy and Big, but took particular issue to the show's portrayal of Sonic, which he summarized as: "'I'm gonna run around downtown until something exciting happens and use a stinking Ring to defeat my enemies'".

[76] In contrast, writer Gaz Plant of NintendoLife opined that "one of the key successes" of the series was its incorporation of numerous characters from the games, including lesser-used ones like Big and the Chaotix.

Famitsu offered a uniformly positive review before the first episode broadcast in 2003, commending the skillful transition of the games' speed and style to animation, and expected the series to continue to grow more interesting.

[3] Plant acclaimed the character development that built on the stories of the original games, especially Sonic and Amy's relationship and the Chaotix's newfound viability as comedy devices.

Concurrently, he found the show "surprisingly touching," particularly in its "emotional" final climax, and favorably compared the space exploration of season three to Star Trek.

[16] Common Sense Media gave it three stars out of five and, while not commenting further on its quality, stated that it was appropriate for grade-school children but that some violent scenes were inadvisable for younger viewers.

[79] The show was quite popular in the United States, France, Indonesia and Malaysia, consistently reaching the number-one position in its timeslot in those countries.

[83][84] Extending over a decade past the show's initial release, the show has spawned internet memes and the phrase "gotta go fast", the title of the song that plays in the opening and closing sequence, has been used in the titles of video game periodical articles to represent the Sonic series[85][86] and other fast-paced video games.