Code Lyoko - Season 1 (2004)

Sissi has found something very special and dear to Ulrich, his diary! Unfortunately the diary contains some information on X.A.N.A. and Lyoko. Sissi decides to use this as a means of blackmail to get with Ulrich. Later Odd, Ulrich, Sissi, and some of the other students are going to a pool, the bus that their riding in is X.A.N.A.'s next target. He wants to ram the bus into a chemical plant. Now the team must head to Lyoko to help Aelita get to the tower to save the students and the rest of the city.

Crashing the city's communications device with a virus, X.A.N.A. jeopardizes thousands of citizens when he runs a pair of trains on a collision course, one of which contains dangerous chemicals. Meanwhile, Odd gets in trouble with the Kadic administration when Sissy reveals the existence of Kiwi to Jim.

Jeremie is working on the materialization program, and Odd accidentally finds it, but it can be used only one time. Jeremie wants to materialize Aelita, but realizes that preparations need to be made. That night, X.A.N.A. possesses two bulldozers and starts to destroy the factory. Odd and Yumi go into Lyoko where she falls into a virtual black hole. In order to save Yumi's life, Jeremie has to choose between either materializing her or Aelita.

Yumi is held captive in Lyoko while her evil clone attempts to destroy the heroes. Meanwhile, an unsuspecting Jeremy sends Odd and Ulrich to Lyoko to help Aelita deactivate a tower, but he ends up alone, face-to-face with XANA.

A movie director begins filming in our heroes' factory, so Ulrich works on the film to make sure no one discovers their secret. But that will be no easy task when XANA takes control of an alien monster prop intent on destroying the heroes.

When all the students' cell phones goes off in class, it starts Sissy on a petition to save her cell phone--but it goes awry when Odd breaks into the school's office's locker to get his, Ulrich's, & Yumi's cell phone. It turns out that X.A.N.A. is trying to get out board a highly powerful military satellite in space. X.A.N.A.'s target turns out be our heroes.

Around the same time that Jeremie loses contact with Aelita, a new student named Taelia resembling her arrives to Kadic. Believing that Taelia is Aelita with amnesia, Jeremie reveals the existence of Lyoko to her. Meanwhile, X.A.N.A. possesses samurai armor that Yumi had brought to school for a presentation.

When the gang learns that if Jeremy passes a few tricky quizzes, that he'll get transferred to another school, they quickly seek a way for him to stay, even if it means failing the test on purpose. Meanwhile, XANA gains possession of a pack of rats, using them to attack the flow of power in the city as well as his earthbound enemies.

Ulrich is fussing over a mysterious letter found slipped under his door one night... a love letter signed by Yumi! Meanwhile, XANA infects a hive of hornets and is using it to attack our heroes. Ulrich struggles with his feelings and how to tell Yumi how he feels about her; that is, if he can figure it out himself, and saving the day from XANA in an episode of life and death.

Jeremy has trouble materializing Aelita, and actually makes matters worse. While he tries to de-bug her program, XANA launches his latest attack, putting Odd in grave danger. Our heroes must decide: Defeat XANA or sacrifice Aelita?

XANA takes control of the factory and traps Yumi, Ulrich and Sissi in the elevator, which plummets to the ground and begins filling with water. Yumi escapes and gets help from Odd and Aelita to deactivate a tower on Lyoko before they drown.

XANA unleashes an attack of laughing gas on the school, inducing fits of laughter which leave our heroes dangerously short of breath. While they try to thwart XANA's latest scheme, Yumi is concerned about her parents who are about to visit.

X.A.N.A. short-circuits the Kadic cafeteria in order to trap Odd, Ulrich, and a bunch of students in an electrified prison. Jeremie, Yumi, and Aelita race to deactivate the tower before it is too late. Meanwhile, Herb becomes jealous of a new student named Theo who is via for Sissi's affection.

XANA creates viruses which attack human brains, causing amnesia. Sissi takes advantage of this and convinces Ulrich that Odd, Yumi and Jeremy are his enemies. Now they must battle their friend and find a way to reverse the viruses.

A new song Odd downloads sends him into a coma, and the same song is passed through the school. XANA's new beat is the cause, and he can broadcast it anywhere. The hospital is full to bursting with cases, and Odd's heart gets weaker with every beat it makes. But when the tune starts playing in the factory, will the crew learn that music can do more than just soothe the soul? And, will Aelita be able to save the crew? It's all up to a leap of faith...

Jeremy convinces Yumi to send him to Lyoko so he can speak in-person with Aelita, but when she hits the wrong key, he becomes stuck between worlds. While they struggle to bring Jeremy back, XANA unleashes a deadly attack on Aelita.

Both Herb & Jeremy are in a robot competition, Herb with "Iron Sissy", and Jeremy with "Kiwi 2". Herb cheats by launching a gear from Sissy to destroy "Kiwi 2". Meanwhile, Xana's latest plan is using the factory to built a robot. Ulrich & Yumi get help from Herb in slow down Xana's robot. Jeremy discovers that Xana's robot was built in the factory and has messed with the computer that goes to Lyoko.

XANA creates an ever-increasing zero-gravity zone on the field during the Kadic soccer final, forcing Ulrich to decide whether to stay with his teammates on the soccer field, or help his friends battle the super computer in Lyoko.

Tired of the same old routine of fighting X.A.N.A., Ulrich decides it's time for a change, which leads to strife between him and Yumi. Meanwhile, X.A.N.A. infects himself with a virus in order to disrupt the scanner program. This will lead the warriors to their death if they can't stop him.

In preparation for a secretly-planned dance party at Yumi's house, Odd gets in trouble with the Kadic administration when he covers up the attempted theft of a computer by his friend, Sam. Meanwhile, X.A.N.A. alters the city's earth level in an attempt to bury his enemies.

XANA traps Ulrich, Odd, and Yumi in a virtual universe and they don't realize there's a fake Jeremy with them who is intent on destroying them. The real Jeremy must now save his friends single-handedly before it's too late.

As Jeremie is perfecting his materialization program for Aelita, Yumi, Ulrich, and Odd are making preparations for her arrival. But as success comes within their grasps, Jim's paranoia aggravates the already bad situation started by X.A.N.A. Due to his injured ankle Jeremie has no choice but to reveal the existence of Lyoko to Jim so he can get to the warehouse.

When Jeremie discovers a fatal connection between a materialized Aelita and the supercomputer, the gang realizes that they will have to postpone their attempts of ridding the world of X.A.N.A. Meanwhile, the corrupted supercomputer decides to engage the warriors in the real world by materializing his monsters for the first time.