The very first season of Code Lyoko originally aired from September 8, 2003 to February 25, 2004. The head writer was Sophie Decroisette. It was directed by Jérôme Mouscadet.
Plot
The first season of the series focuses more on character development than plot development, only revealing details about the plot in its last few episodes. The rest of the episodes are "filler" because in each episode, the Lyoko Warriors discover a X.A.N.A. attack, fight against it, stop it and activate a Return to the Past for one single day.
As a complement to avoid monotony of the series, this season shows relationships between characters and other students and teachers of the school with their parents, relatives, etc. During all this, Jeremie is working on a program to "materialize" Aelita (transport her from the virtual world to the real world) so that they can turn off the supercomputer and, therefore, X.A.N.A. once and for all.
Story
X.A.N.A. Awakens
X.A.N.A.'s first attack.
As Jeremie Belpois is looking for parts to use for his robots in an abandoned factory, he eventually finds the supercomputer and restarts it. Aelita awakes almost immediately afterwards, but didn't remember anything about her past. Jeremie assumed she was an artificial intelligence and decided to name her Maya, after she requested to be called something other than "Artificial Inteligence". As Jeremie found out about the scanners and virtualization, he sent Odd Della Robbia and Ulrich Stern to Lyoko. They didn't meet Aelita because they were devirtualized by Bloks in the Ice Sector, but not before Ulrich spots a strange red Tower in the same Sector. Feeling the pulsation from the red tower, Aelita heading to the Ice Sector through a Way Tower.
Jeremie wanted to fully materialize Aelita on Earth, so they can shut down the supercomputer and neutralize X.A.N.A. for good. He had confided in Odd, Ulrich and Sissi that they could do it if they could get Aelita into the red tower (a tower which X.A.N.A. had activated when Jeremie restarted the supercomputer) in the Ice Sector. However, Sissi gets electrocuted by an electric energy orb sent by X.A.N.A. and Ulrich brings Yumi Ishiyama to the factory. Jeremie sends Ulrich, Odd and Yumi to Lyoko to help Aelita get to the tower after an fierce fight with X.A.N.A.'s monsters. As Aelita saw the interface, she found out that her name wasn't Maya, but Aelita. She deactivates the tower. However, Jeremie's theory was wrong as Aelita didn't come to Earth. Aelita thinks that keeping the supercomputer on is too dangerous and that they should shut it down immediately, but the others agreed to keep fighting X.A.N.A until Jeremie finds a way to materialize Aelita. (X.A.N.A. Awakens)
Aelita's Materialization Program
Jeremie programmed an almost working version in Cruel Dilemma. But it wasn't until he left, and Odd accidentally pressed a few keys that weren't known, which made the program workable. Since nobody knew the full contents of the program, it couldn't be recreated. For an unspecified reason, it wasn't re-usable. Because of these two facts, it was a single-use program. Yumi fell into the Digital Sea later in the episode, and they had to use the program on her instead. This version was the only Materialization program that was able to recover a body from the digital sea. Unlike the later versions, it didn't require the target to be in a Tower to work. In Just in Time, Jeremie managed to create a materialization program which actually worked. Since he was unsure if it would work correctly or not, he tested it by materializing a single hair of hers. This worked, but in the process, his program bugged up the Annex Program, so that if Aelita used Code: Lyoko, she would be deleted. Exactly that happened, so the group used the hair to clone her and recover her data. In Frontier, when Aelita and Jeremie try to do more tests on materialization, Aelita accidently does some preparations that Jeremie had already done, causing Jeremie to get mad at her. As Jeremie thinks he hurt Aelita, he decides to go into Lyoko by himself, but an error occurs, moving Jeremie somewhere between Lyoko and Earth. Aelita, who is connected to Jeremies' thoughts, activates four towers from four sectors, bringing Jeremie safely back to Earth just before the supercomputer had him erased. During Ghost Channel, Odd, Yumi and Ulrich dissappeared during Return To The Past. Aelita finds out that X.A.N.A had created a virtual reality to trick the missing trio into thinking that they were actually back in the real world. As Jeremie virtualized himself to save the others, Aelita used her abilities to destroy the illusion, freeing the others from X.A.N.A.'s mercy. (Cruel Dilemma, The Girl of the Dreams, Just in Time, Frontier, Ghost Channel)
Aelita is finally Materialized
Aelita finally materialized.
In Code: Earth, Jeremie soon manages to create the correct materialization program, sending Aelita to the Forest Sector. However, monsters attack her and the tower she is in in order to stop her from leaving. But with the help of Ulrich, Aelita materializes for the first time on Earth with others being at the scanner room to welcome her. Jeremie had her enrolled to Kadic as Odd's cousin and Yumi had her parents convinced about her staying at her home and Aelita was even better than Jeremie in the classes. But when team tried to shut down the supercomputer, Aelita collapses. As Jeremie investigated, he found out that X.A.N.A. had giving Aelita a virus that connects them both. If X.A.N.A. is destroyed, so is Aelita. With X.A.N.A. sending his monsters to attack Kadic, Aelita deactivates the tower and decides to stay in Lyoko in case X.A.N.A. would attack again. The Lyoko Warriors decide that Aelita would visit the Earth occasionally to visit for them. (Code: Earth, False Start).
Episodes
| Ep No. | Pro No. | Name | Image | French Title | Airdates |
| 0 | N/A | X.A.N.A. Awakens, Part 1 | 
| Le réveil de XANA partie 1 | US: October 2nd, 2006 FR: October 21st, 2006 |
| 0 | N/A | X.A.N.A. Awakens, Part 2 | 
| Le réveil de XANA partie 2 | US: October 3rd, 2006 FR: October 21st, 2006 |
| 1 | 101 | Teddygodzilla | 
| Teddygozilla | US: April 19th, 2004 FR: September 3rd, 2003 |
| 2 | 102 | Seeing Is Believing | 
| Le voir pour le croire | US: April 20th, 2004 FR: September 10th, 2003 |
| 3 | 103 | Holiday in the Fog | 
| Vacances dans la brume | US: April 21st, 2004 FR: September 17th, 2003 |
| 4 | 104 | Log Book | 
| Carnet de bord | US: April 22nd, 2004 FR: September 24th, 2003 |
| 5 | 105 | Big Bug | 
| Big bogue | US: April 23rd, 2004 FR: October 1st, 2003 |
| 6 | 106 | Cruel Dilemma | 
| Cruel dilemme | US: April 26th, 2004 FR: October 8th, 2003 |
| 7 | 107 | Image Problem | 
| Problème d'image | US: April 27th, 2004 FR: October 15th, 2003 |
| 8 | 108 | End of Take | 
| Clap de fin | US: April 28th, 2004 FR: October 22nd, 2003 |
| 9 | 109 | Satellite | 
| Satellite | US: April 29th, 2004 FR: October 29th, 2003 |
| 10 | 110 | The Girl of the Dreams | 
| Créature de rêve | US: April 30th, 2004 FR: November 5th, 2003 |
| 11 | 111 | Plagued | 
| Enragés | US: May 3rd, 2004 FR: November 12th, 2003 |
| 12 | 112 | Swarming Attack | 
| Attaque en piqué | US: May 4th, 2004 FR: November 19th, 2003 |
| 13 | 113 | Just in Time | 
| D'un cheveu | US: May 5th, 2004 FR: November 26th, 2003 |
| 14 | 114 | The Trap | 
| Piège | US: May 6th, 2004 FR: December 3rd, 2003 |
| 15 | 115 | Laughing Fit | 
| Crise de rire | US: May 7th, 2004 FR: December 10th, 2003 |
| 16 | 116 | Claustrophobia | 
| Claustrophobie | US: May 10th, 2004 FR: December 17th, 2003 |
| 17 | 117 | Amnesia | 
| Mémoire morte | US: May 11th, 2004 FR: December 24th, 2003 |
| 18 | 118 | Killer Music | 
| Musique mortelle | US: May 12th, 2004 FR: December 31st, 2003 |
| 19 | 119 | Frontier | 
| Frontière | US: May 13th, 2004 FR: January 7th, 2004 |
| 20 | 120 | The Robots | 
| L'âme des robots | US: May 14th, 2004 FR: January 14th, 2004 |
| 21 | 121 | Zero Gravity Zone | 
| Gravité zéro | US: May 17th, 2004 FR: January 21st, 2004 |
| 22 | 122 | Routine | 
| Routine | US: May 18th, 2004 FR: January 28th, 2004 |
| 23 | 123 | Rock Bottom? | 
| 36ème dessous | US: May 19th, 2004 FR: February 4th, 2004 |
| 24 | 124 | Ghost Channel | 
| Canal fantôme | US: May 20th, 2004 FR: February 11th, 2004 |
| 25 | 125 | Code: Earth | 
| Code Terre | US: May 21st, 2004 FR: February 18th, 2004 |
| 26 | 126 | False Start | 
| Faux départ | US: May 24th, 2004 FR: February 25th, 2004 |
Trivia
- If one adds the two-part prequel, X.A.N.A. Awakens, then the first season consists of 28 Episodes rather than 26.
- This was the only season of not made by Moonscoop. It was made by Antefilms, prior to their merger with France Animation.
- This season had more English DVD releases than the other seasons combined. In fact, the entire season, has been released by two companies. In addition, 3 partial sets have been released.
- The Desert region has the most appearances.
- Despite not being able to defend herself, Aelita's special ability is "creativity", the earth-based power to manipulate and alter the terrain of all four ecological regions of the virtual world.
- Odd Della Robbia's only ability on Lyoko is "future flash", allowing to see imminent danger to his friends or hidden paths. It is used only in four episodes and is lost after this season.
- The ever-suspicious Jim Morales temporarily joins Team Lyoko, but has his memory wiped by a return to the past.
