The BEST Episodes of Code Lyoko
Every episode ever - ranked by fan votes!
Last Updated: Nov 27, 2019
Network: Cartoon Network
Code Lyoko tells the story of a group of students who uncover a parallel universe called Lyoko inside a super-computer, which entraps a malevolent sentient AI called X.A.N.A.
#1 - A Bad Turn
Season 2 - Episode 13
When Ulrich tries to tell Yumi how he really feels after some prodding by the rest of the group, he finds her talking to William, who is doing the same thing Ulrich had planned to. Yumi turns him down, but Ulrich leaves before hearing it. Meanwhile, Xana activates a tower and materializes a Krabe. At school, a driving class has been set up to teach the kids road safety. William turns out to be a good driver and Ulrich a rather poor one, which William makes fun of him for. The two then get into a fight and get detention because of it. Jeremie learns of the activated tower shortly after and the group heads to the factory without Ulrich. During this time, the Krabe makes its way to Yumi's house. When the group reaches the factory, they find a second Krabe guarding it. Yumi learns of the first Krabe from Hiroki and goes to help while Odd distracts another Krabe so they can get to the elevator. In the scanner room, they learn that the first two Krabbes destroyed the scanners that produced them, leaving just one usable. Aelita goes to Lyoko first. Before Odd can go, however, a third Krabe is materialized, preventing any further use of the scanners. Now Odd has to deal with this Krabe, Ulrich and William have to deal with the second, and Yumi and her family have to deal with the first. Not only that, but Aelita has to make her way to the tower without any support, and makes a decoy for the Scyphozoa.
8.22 
#2 - The Pretender
Season 3 - Episode 6
Odd and Ulrich are talking in the shower room when a young boy, Johnny, asks to talk to Ulrich. It turns out that Johnny likes Yumi, and being jealous of that, Ulrich tells him to follow her around to get her attention, which Yumi hates. After following her all day and ending up in the gym, a flock of crows possessed by Xana attacks Yumi. She is beaten unconscious by their electrified beaks and sent to the hospital. Meanwhile, as Jeremie and the others are fighting monsters to deactivate the tower, the Scyphozoa possesses Aelita and has her enter Code:XANA into the way tower, wiping out The Desert Sector for good and leaving Lyoko with two main Sectors - The Mountain Sector and The Ice Sector. Once Jeremie finds out, he activates a return to the past with strong hope for Yumi's life. This episode proves that Ulrich is not as comfortable as being just friends with Yumi as he says he is.
8.20 
#3 - Exploration
Season 2 - Episode 3
After discovering The Carthage Region, the group decides to explore it. Yumi is forced to opt out after her continued late-night trips to Lyoko draw the attention of her parents. While on The Carthage Region, Ulrich and Odd get dematerialized but don't appear in the real world, so Yumi sneaks out of the house to go to Lyoko and rescue Aelita from the Scyphozoa while Jeremie searches for a way to recover Odd and Ulrich. Unfortunately, Yumi's parents discover that she is missing and alert the school, who in turn discover that the other four are missing as well.
8.10 
#4 - The Chips Are Down
Season 2 - Episode 9
When Ulrich learns that Yumi might have to go back to Japan because her father lost his job, he can't accept losing her. After hearing the lottery numbers on the radio though, he gets an idea. Using a return trip, he is able to get a ticket with the winning numbers and give it to Mr. and Mrs. Ishiyama. When the others find out, they kick him out of the group until they can figure out what to do. To make matters worse, Xana activates a tower and possesses Nicolas. On top of that, he creates an army of Krabs to guard it.
8.00 
#5 - Sabotage
Season 3 - Episode 9
When Xana sabotages the supercomputer, weird bugs begin cropping up in Lyoko. With its power rapidly draining, Jeremie needs to repair it before it becomes completely useless. However, he seems to forget about boys' dorm inspection, so Jim forces him to stay behind. Meanwhile, Xana possesses vines to trip up the rest of the group, except Aelita. Since the attack keeps draining power from the supercomputer, Aelita purposefully wipes out The Ice Sector leaving The Mountain Sector left.
8.00 
#6 - Attack of the Zombies
Season 2 - Episode 14
When Xana possesses Kiwi, it turns the little dog into the carrier for a virulent virus that turns those it infects into zombies. To make matters worse, Aelita and Jeremie are stuck in the cafeteria and can't get to the factory. On top of that, Odd is a zombie himself. Jermie and Aelita escape but Ulrich and the other students (except William, who is turned into one himself) fight the rest.
7.89 
#7 - Fight to the Finish
Season 4 - Episode 29
With the Skid gone and XANA's Replikas at unmanageable numbers, Jeremie continues work on his multi-agent system. Meanwhile, Aelita has nightmares about her father being killed by XANA. As Jeremie works, he is contacted by Franz Hopper, who arranges a meeting on Lyoko. William wants to help, but all except Aelita are a little wary of trusting him again. William is left in the lab with Jeremie. After meeting up, Franz transmits the data necessary to finish Jeremie's multi-agent system. However, XANA is not willing to give up without a fight, activating a tower to possess William once again while sending the Kolossus to deal with Franz. Yumi willingly devirtualizes herself and fights William while the others protect Franz. Once Franz is finished transmitting the data, Aelita and Odd head to Sector Five to finish the program. Ulrich, meanwhile, manages to defeat the Kolossus, but its corpse falls on Ulrich, devirtualizing him instantly. However, a problem arises: the energy requirements are too great. Aelita's nightmare is realized when Franz makes the ultimate sacrifice himself to power the program, and in doing so XANA is wiped out completely. Though a great victory for them, the loss of Franz Hopper leaves them with little reason to celebrate.
7.89 
#8 - Distant Memory
Season 4 - Episode 17
It's holiday time at Kadic and everyone is headed home. Aelita, however, has no home to go to. As she watches over Lyoko, she gets a message from Franz Hopper, who has constructed a simulation bubble of their mountain home on Lyoko. Though happy to see her father, Aelita quickly learns that the entire thing is a trick from xana - her father is just a mirage, and William is there waiting for her to throw Aelita in the digital sea Williams say(impossible to escape this bubble as it is your prison) The rest of the group, having been unable to contact Aelita, follows her onto Lyoko, but they fail to keep William from throwing her into the digital sea. When it seems as if she's gone, she is lifted from the sea by the real Franz Hopper, who has manifested himself as a floating blue bubble with a pink aura. After dropping her back on Lyoko, he returns to the digital sea.
7.88 
#9 - Cousins Once Removed
Season 4 - Episode 23
Jeremie's cousin, Patrick, comes to visit. Jeremie isn't entirely happy about it, since Patrick is "super cool" compared to him. Discovering another Replika, Jeremie and his friends plan a mission to destroy it, leaving Sissi alone with Patrick. She is able to convince him to let Herve rummage through Jeremie's computer files. Herve discovers Aelita's forged documents and the program running the Skid, his efforts to decipher it inadvertently draining the Skid's power. To make matters worse, XANA possesses both him and Sissi to cause even more damage. Jeremie, meanwhile, deduces that it's his computer back at school causing the damage, and works with Patrick to stop them. Once the attack has passed, Jeremie has Aelita run a return trip to undo the damage caused. The second time around, Jeremie is a bit more appreciative of his cousin, since the two worked well together before. But, unfortunately Patrick goes back to his own school.
7.88 
#10 - Wrong Exposure
Season 4 - Episode 25
Aelita finds a photo of herself with Franz Hopper at the Hermitage, with a mathematical equation in the background. Jeremie discovers that the program works as a reset feature to Lyoko, something not too helpful but useful nonetheless. Meanwhile, Odd, in an attempt to impress a girl in photography class, inadvertently sends the photo to Sissi, who in turn shows it to her father. He questions the group about it, with Jeremie pointing out that Aelita would obviously be twenty-four by now if she were the one in the photo. They are sentenced to dentention in the library by Jim before any more discussion occurs. Before he can follow up on the matter, Jean-Pierre possessed by XANA. He delivers Aelita to Lyoko, where the Scyphozoa is waiting for her. It takes control of her and tries to force her to walk into the digital sea, but Ulrich and Yumi are there to keep her from doing so. As they battle Aelita and the monsters, Jeremie uses the reset program, clearing Aelita's possession and allowing her to deactivate the tower. After performing a return trip, Aelita explains that her real last name isn't Hopper, it's Schaeffer (the name listed on the folder in the end credits). Hopper is the last name of her mother, Antea. In addition, Franz's supposed first name is actually his middle name. Franz appearently changed both his and Aelita's names when they moved to the Hermitage in order to have a fresh start.
7.88 
#11 - Frontier
Season 1 - Episode 19
When Jeremie yells at Aelita, he tries to go to Lyoko to apologize. Unfortunately, while Yumi is transferring him, she makes a scanner error, which leaves him trapped in a virtual limbo between Lyoko and the real world, so Aelita has to retrieve data to recover Jeremie without support in order to bring Jeremie back, but when she gets to the Mountain Sector, there are a couple of Blocks guarding the tower. Yumi is sent to retrieve Jeremie's laptop to virtualize Ulrich, but gets caught and ends up in the principal's office. Ulrich talks to Sissi to see if she could get Yumi off the hook; Sissi agrees, but only if Ulrich will go out with her for a month. Ulrich agrees on one month and kisses her as a down payment.
7.82 
#12 - The Key
Season 2 - Episode 26
After going through all of Franz Hopper's diary, Jeremie discovers the truth behind the supercomputer, at least to some extent. Hopper had used it quite extensively, to the point of repeating a single day for more than seven years. His sanity degraded throughout the experience. Hopper also revealed that he and Aelita hold the keys to Lyoko, which Xana was after. He only needed her half, now. The keys would allow him to escape the supercomputer. Jeremie also finds a way to free Aelita from the supercomputer. It turns out that Aelita never had a virus. In fact, Xana had been holding onto a piece of her, which was responsible for linking her to the supercomputer. Aelita is not willing to go, angry over the fact that Hopper had essentially taken her life from her. She's also worried that Xana might escape. To that end, she shuts down the supercomputer. Jeremie rescues her, and the group goes to Lyoko to retrieve her fragment. After all their efforts, they seem to succeed, but it turns out to be a fake. Xana manages to devirtualize Aelita's defenders and steal her memory, effectively killing her and allowing him to escape, which shuts down Lyoko in the process. His escape allows Franz Hopper to revive Aelita and Lyoko, restoring all of Aelita's memories in the process. Through the restoration, Aelita finally remembers her past up to the point that she went to Lyoko. With Xana now free and Aelita's memories returned, neither are linked to the supercomputer. This means that they could shut it down, but it would do no good. Unsure of how they'll proceed, Jeremie promises that they'll find a way to stop Xana.
7.80 
#13 - Mister Puck
Season 2 - Episode 5
When Aelita's dreams and hallucinations become too disruptive to ignore, the group heads to the Hermitage to discover their source. There, Aelita finds a doll she inexplicably recognizes to be Mister Pück. Hidden on this doll is a key to a train station locker, which contains the heavily encrypted diary of Franz Hopper. Upon its discovery, Xana takes action, possessing Jeremie, to ensure they'll never be able to read it. When they deactivate the tower and Jeremie comes to his senses, Yumi explains to Jeremie why Xana can possess him and not Ulrich, Aelita, Odd, or Yumi.
7.80 
#14 - Teddy Gozilla
Season 1 - Episode 1
Milly and Tamiya are doing a report on the school prom. They try to interview Sissi, who was prom queen last year, but she turns them down and makes fun of their age. Milly tries to ask Ulrich out, and he turns her down because he's going to the dance with Yumi. Upset, Milly storms off. In her room, she tells Tamiya that she hates everyone, with X.A.N.A. listening from her computer. When Milly tells her teddy bear that she wishes she were bigger and leaves it in the garden shed, X.A.N.A. possesses it and uses it to attack those who had made fun of her. It then increases the teddy bear's size to roughly two stories and sets it on the town. Since Ulrich had to protect the school and warn Yumi, it's up to Odd go to Lyoko and help Aelita deactivate the tower and protect the rest of the town from the rampaging teddy bear. After a return to the past, Milly asks Ulrich to the dance again, and Ulrich says yes, embarrassing Sissi.
7.75 
#15 - Franz Hopper
Season 2 - Episode 23
Jeremie discovers five activated towers and gathers the group to take care of them. However, when they arrive at the factory, they find a man at the interface, deactivating the towers as if it were a simple matter to do so. When questioned, the man claims that he's none other than Franz Hopper. However, something seems off about this convenient arrival. Franz says that the scanners cause cell degeneration, and blames it and the destruction of his diary on Jeremie. With everyone except Aelita angry at him, Jeremie calls his father and asks to be withdrawn from Kadic in favor of a school for gifted students – but after he hangs up, while pondering his dilemma, he realizes that there is something inherently wrong with Franz's explanation.
7.75 
#16 - Code: Earth
Season 1 - Episode 25
Jeremie finally completes his materialization program and prepares to bring Aelita into the real world. At the same time, Jim's suspicions of the group have risen to the point that he's actively trying to discover their secret and he ends up causing Jeremie to injure his ankle while running away from him down stairs in the school.
7.75 
#17 - Just in Time
Season 1 - Episode 13
Taking a different approach to his research, Jeremie materializes a single hair of Aelita's. Unfortunately, the follow-up test goes awry, and Jeremie has to find out why. Meanwhile, different parts of the school begin to crumble apart. Jeremie learns that his first test damaged Aelita's program, and she'll be deleted if she tries to deactivate a tower. On top of that, they learn that X.A.N.A. is responsible for the damage being caused to the school by using ultrasonic sound waves, which continues to get worse. Jeremie has to fix the damage he caused in time to save Odd, who ends up trapped inside the school with Milly, Tamiya, and Kiwi. Unfortunately, after two tries, both ending in failure, Aelita, with the help of Yumi and Ulrich, has to deactivate the tower or else Odd, Milly, Tamiya, and Kiwi will be done for. After the return back in time, Yumi remembers that Jeremie said that the hair contained Aelita's entire computer code. Jeremie places the hair in the scanner, virtualizes it to Lyoko, and Aelita is inside the tower she deactivated.
7.71 
#18 - New Order
Season 2 - Episode 1
After discovering Aelita's link to the supercomputer and the inability to shut off the supercomputer that stems from it, Jeremie works hard to find new and better ways to fight Xana. To that end, he develops new vehicles for the group. He also develops a new tower-scanning program that instantly detects activated towers, allowing Aelita to live on Earth. While adjusting to her new life, the class takes a trip to the nearby woods for a scientific field trip. Ulrich wants to partner up with Yumi, but she's already partnered up with someone named William.
7.70 
#19 - A Great Day
Season 2 - Episode 4
After taking another trip to The Carthage Region and returning to the school, Aelita talks to Jeremie about not being human, unaware that Sissi is recording their conversation. On top of that, the data they had retrieved from the Carthage Region takes over the supercomputer and starts running return trips over and over. Jeremie discovers that returning to the past makes X.A.N.A. much stronger and more powerful. During the third return trip, Xana possesses Sissi with his newly strengthened and increased abilities and powers and goes after Ulrich. Not only does the group have to deal with Sissi, but they also have to stop the return trips from continuing.
7.70 
#20 - The Trap
Season 1 - Episode 14
It's been a year since the group first discovered the supercomputer and Aelita, and they decide to throw a surprise party for Aelita. Sissi catches wind of the party and follows Ulrich and Yumi to the factory. On the way there, X.A.N.A. possesses the factory as a whole. Jeremie and Odd are the first to arrive at the factory, finding the elevator to be inoperable. They head off to find the fuse box. Once Ulrich and Yumi arrive there, Sissi confronts them about it. They tell her to leave, but X.A.N.A.'s earlier possession allows him to trap all three in the elevator and drop them to the bottom of the shaft. Sissi and Yumi come out okay, but Ulrich's arm is broken in the fall. Meanwhile, Jeremie and Odd have to deal with the possessed factory equipment. Odd, Yumi, and Jeremie are safe and are at the supercomputer room. While Yumi and Odd are getting virtualized, water from the pipelines inside the walls is falling on the elevator, causing it to overflow. While the elevator is halfway filled, Ulrich promises to Sissi that if they make it out alive, he would be nicer to her. When Ulrich and Sissi are about to drown, Aelita deactivates the tower just in time and the return to the past saves them both. Just like Ulrich promised, he is nicer to Sissi at the end.
7.69 
#21 - Ghost Channel
Season 1 - Episode 24
After another successful battle against X.A.N.A. and another return trip, Ulrich, Odd, and Yumi are nowhere to be found. They, however, do not see anything wrong with where they are. X.A.N.A. has trapped them in a world of its own design, which is fashioned after the school to ease their suspicions. Meanwhile, in the real world, Jeremie is being questioned on the group's disappearance. However, the world that Ulrich, Odd, and Yumi are in appears to have some glitches in it. Jeremie finds that this world can be accessed through the scanners, and after a near-death with X.A.N.A.'s virtual zombies, Aelita manages to save them.
7.67 
#22 - Triple Trouble
Season 3 - Episode 11
When Odd complains that he doesn't have any cool powers on Lyoko like his friends, Jeremie designs him a teleportation power. It works, but ends up leaving duplicates of himself in the location he teleported from in The Mountain Sector. After trying it twice, Jeremie devirtualizes Odd to find out what went wrong, accidentally creating three clones. Meanwhile, in the real world, Xana attacks using a mysterious smoke that turns anyone it hits to stone. One of Odd's copies gets turned to stone, so the other two Odds must retrieve him before they become unstable and disappear.
7.67 
#23 - Crash Course
Season 4 - Episode 7
Jeremie decides to teach Odd, Ulrich, and Yumi how to use the supercomputer in case he or Aelita are unable to, being XANA's favorite target. During the lesson, Jeremie is attacked by one of XANA's polymorphic clones, leaving the others to operate the supercomputer without help. Aelita is at the final audition with the Subdigitals, competing against two other candidates, and thus cannot be contacted. To make matters worse, the clone heads for her after dealing with Jeremie. Using what they learned from Jeremie, the others are able to rescue Aelita and deactivate the tower without his help. Aelita is also chosen as the winner of the audition despite her walking out on them.
7.67 
#24 - A Lack of Goodwill
Season 4 - Episode 16
Jeremie has developed a program to make the William clone smarter, but the learning curve is still problematic, as it tries to fling a glass into the air from a fork. Milly and Tamiya, overhearing the group's conversation about the clone, decide to ask him personally. The clone, having never been told to keep the information a secret, reveals everything to them, and even takes them to the factory. Meanwhile, Jeremie plans a mission to the next Replika, a copy of the Desert Sector. During the trip, William emerges from a scanner and tries to destroy the supercomputer. With the help of Milly, Tamiya, and the William clone, he is defeated, and a return trip keeps Milly and Tamiya in the dark about the supercomputer.
7.67 
#25 - Saint Valentine's Day
Season 2 - Episode 6
It's Saint Valentine's Day and love is in the air. Ulrich forgets, so at last minute writes a poem for Yumi. However, when William presents Yumi with flowers, Ulrich gets jealous and reads the poem to Sissi instead, hoping to elicit jealousy from Yumi. The two end up in a fight, both bothered and wondering if the other really likes them. Also, a man possessed by Xana leaves a necklace at Aelita's door, Aelita is convinced that it was Jeremie who got it for her. Since Jeremie didn't actually get it, he's left to wonder who did, and ends up suspecting Odd, who avoids the question. This puts the two at odds, so to speak. Meanwhile, Aelita's necklace takes control of her and forces her to deliver herself to the Scyphozoa. Luckily, Odd arrives in time, and is able to save Aelita from the Scyphozoa by "threatening" to kill her.
7.67