Upon activating it, he discovers a virtual world called Lyoko with an artificially intelligent girl named Aelita trapped inside it.

and aided by his three friends, Odd Della Robbia, Ulrich Stern, and Yumi Ishiyama, who are virtualized into Lyoko to save both worlds from the evil virus.

Once the Tower is deactivated, Jeremy can launch the "Return to the Past" program, which sends the world back in time to undo any damage caused by X.A.N.A., while anyone scanned into the Supercomputer retains their memory of the events.

In Season 2, Aelita adjusts to life in the real world, while Jeremy attempts to develop an antivirus program to liberate her from X.A.N.A.

The gang begins to uncover information about a mysterious man named Franz Hopper, who went missing ten years ago.

Aelita appears to perish as a result but is revived when Franz Hopper restores her completely, along with her missing fragment: the memories of her life on Earth before she was virtualized on Lyoko.

After what they thought was their defeat, Jeremy receives a coded message from Franz Hopper that allows him to recreate Lyoko and continue the fight against X.A.N.A.

's "Replikas," which are copies of Lyoko's sectors that are linked to X.A.N.A.-controlled supercomputers on Earth, all created for its goal of world domination.

[7] French animation company Antefilms took interest in the film due to its atmosphere and offered Romain and Palumbo a contract to turn it into a series.

Similar to its succeeding show Code Lyoko, Garage Kids was originally envisioned as a 26-episode miniseries detailing the lives of four French boarding school students who discover the secret of the virtual world of Xanadu; created by a research group headed by a character known as the "Professor".

[3] Anime also served as inspiration, specifically Serial Experiments Lain for its "worrying digital dimension" and Neon Genesis Evangelion for its dangerous entities to fight.

[3] While incorporating it, Palumbo and Romain wanted to avoid making the series "too playful and superficial" and sought to "get around the censoring done by TV channels that tend to soften youth programs" by writing episodes "with tension, suspense, even tragic scenes.

[3][10] Palumbo and Romain were adamant on keeping the locales based on "the France we knew", as they wanted to avoid what they perceived as "fantastical" or "Americanized" locations other French cartoons used at the time.

[3] Scripting for the series officially began in January 2002, with Frédéric Lenoir, Françoise Charpiat, and Laurent Turner being brought on as writers.

[14] Progress was slow over the summer of 2002, which Mouscadet attributed to the series' head writer "[taking] a lot of vacation".

[13] Antefilms reached out to Sophie Decroisette as a replacement, who had recently been a writer for Malo Korrigan and was on a break after giving birth to her first child.

The series' human character designs were primarily influenced by Japanese animator Kōji Morimoto's style.

After the series was sold to France 3 and Canal J, producers felt "Garage Kids" was too unclear for a title and requested it be renamed.

Writing an episode typically lasted 2–3 weeks, though some took longer if higher-ups were unhappy with the story or it ran into issues.

[17] Before Romain left the project, the idea of Lyoko being created by a team of researchers had changed to just one: Franz Hopper.

Decroisette revealed during production of season 4 that the full backstory would not be told in the show, as she considered it "very complicated... dense and [not] really important to the story.

[16] Aside from this, Decroisette otherwise noted that she "never felt censored" while working on the series, apart from a self-imposed restriction to write stories appropriate for children.

[17] Bruno Regeste became head writer for Code Lyoko's final season after Decroisette stepped down while she was pregnant with her second child, though she continued writing scripts and closely monitored episodes involving Replikas.

[18] Starting around the third season, a team dedicated to Code Lyoko was formed at Hong Kong Limited's studio, who were managed on-site by two members from Antefilms' Paris office.

[13] This change stemmed from Mouscadet's desire for a more consistent animation quality, which he described trying to manage it prior to that point as "a little bit like steering an ocean liner with binoculars".

[23] Emily Ashby of Common Sense Media gave the show 4/5 stars, writing: "Kids will like the battles in Lyoko -- each plays out much like a video game", and added: "Strategy and teamwork are themes throughout the series.

[26] The series has achieved international fame as well, becoming the #2 show on Cartoon Network's Miguzi block upon its premiere in the United States.

[29][31] A series of Clan TVE festivals in Spain included live stage shows based on Code Lyoko among other things.

possesses Eva Skinner, an American girl, and travels to France in order to infiltrate the gang and kill them off.

Unaware of their enemy's presence, the group works to find clues about Aelita's past, left by her father Franz Hopper, and confirm whether or not her mother is still alive somewhere, but at the same time, a terrorist group, the Green Phoenix, has become interested in the Supercomputer and intend to use both it and the virtual world of Lyoko for evil purposes.