Code Lyoko - Season 4 (2007)

William is stuck in Lyoko and the clone Jeremy created to replace him in school is elected manager of the school's new recreation room. XANA possesses the clone, causing him to destroy the room and it now poses a threat to the students.

Jeremy and Aelita are close to complete the ship called the skidbladnir which can travel through the world wide web. But when they are found up late and in each others room. They get detention with Jim, how can they watch the progress of the ship and be in detention at the same time.

Jeremy launches the virtual ship Skidbladnir on its maiden voyage. But when a problem arises, Jeremy needs to get his notes from his dorm room and the school is in lockdown for a fire drill, leaving our heroes to face a new menace.

Jeremy tries to teach his reluctant friends how to operate the computer in order to enter Lyoko. While Aelita is away at a music audition, XANA launches an attack and renders Jeremy unconscious, leaving the others to remember their lesson.

The group travels to one of XANA's Lyoko replicas in the digital sea. Meanwhile, Aelita and Odd get into a fight after Odd's desire to sleep in gets them both in trouble. Furthermore, their arguing inadvertently leads Nicolas and Herve into the factory, where Jeremie is forced to distract them while the group explores the Lyoko copy, which consists entirely of the Forest Region. On the Lyoko replika, William and a pair of Megatanks arrive to destroy the Skid, the destruction of which would cut the group off from the supercomputer. Odd and Aelita refuse to work ...

Jeremy convinces the group to attend a commando camp in order to get in better shape for their battles. Soon enough, XANA attacks, with Jeremy and the instructor battling in the real world and everyone else using their new skills in Lyoko.

XANA uses a military laser to send a comet hurdling towards Earth. Meanwhile, Ulrich, Odd and Aelita are deep in the virtual world and unable to return quickly, leaving Yumi, Hiroki and Johnny to somehow save the world.

During a class field trip to an island in the middle of a lake, XANA conjures an aquatic monster to trap the students. However, Yumi, who stayed behind to do her schoolwork, is able to enter Lyoko where she must face William one-on-one.

During an attempt to rescue William and battle XANA's monsters, Yumi becomes stranded in the Digital Sea. If she survives, her brother Hiroki might get killed after she learns he stole her diary and Ulrich found it.

Jeremy develops a new teleportation process and sends Aelita and Odd into the jungle to destroy another super computer. But William learns how to cut off the process, bringing them back to Lyoko to battle his mechanical spiders.

Our heroes return to the jungle to destroy the other super computer but are met on their way by waves of mechanical killer spiders. Meanwhile, Odd has a hard time winning a bet with Ulrich that he will stop bragging for 24 hours.

Odd takes his dog into Lyoko and ends up with uncontrollable dog behaviors in the virtual world. While Jeremy tries to separate them, Yumi battles a real world motorcycle gang possessed by XANA and Ulrich and Aelita battle William in Lyoko.

Our heroes travel to the desert to destroy a hidden super computer but their trip is cut short when the real William arrives in the computer lab. Meanwhile, Jeremy tries to prevent William's clone from being discovered by Milly and Tamiya.

While everyone is gone for the winter holidays, Aelita stays behind to watch for XANA. But she receives a message from her long-lost father inviting her to join him in the virtual world, and she accepts, realizing too late that it's a trap.

Odd breaks a mirror, causing bad luck to follow him everywhere, including Lyoko. As the heroes make another trip to the desert, they hope the bad luck is behind them when face off against an army of XANA's Kankrelats.

Jeremy wins a ride in the back of a military jet fighter, but when XANA takes control of the jet's computer - and its missiles, our heroes must defeat the super computer in the virtual world before the plane and its weapons hit the school.

The beautiful new exchange student is very interested in Odd and he attempts to woo her by showing her the super computer. But when she touches the computer, it creates a series of problems with disastrous results for those in Lyoko.

Odd's dog Kiwi is banished to the factory after another incident at the dorm. Meanwhile, XANA takes control of Jeremy's robot dog, Kiwi2 and turns it into an attack dog, so Aelita travels into Lyoko to deactivate the tower controlling it.

Yumi and Odd travel into outer space on a mission to destroy a newly-discovered super computer with a dangerous defense system. Meanwhile, Yumi's family cares for Odd's dog during a surprise dorm inspection at school.

Jeremy's cousin Patrick visits and problems arise when Patrick lets Herve look at Jeremy's computer. Our heroes' mission is soon compromised and Aelita's fake identity is uncovered. Only a trip back in time can fix this situation.

XANA kidnaps Aelita just before her big night deejaying at the Subdigitals' concert. While her friends battle to save her in the virtual world, Odd is busy looking for an extra ticket that he promised to a girl he wants to impress.

Aelita's secret past is in danger of being revealed when Sissi gets a hold of an old photo of Aelita with Franz Hopper. Meanwhile, Jeremy needs the picture because of the mathematical formulas written on the blackboard in the background.

XANA uses the school's cell phone antenna to spread a virus causing phone users to become evil zombies, including Odd's parents, who are visiting. Our heroes travel through Lyoko to the mountains to stop the virus and reverse its effects.

Odd and Yumi travel to polar Siberia on a mission, only to be confronted by William who has been sent by XANA to stop them. Meanwhile, Ulrich and Aelita confront XANA's latest creature, the massive Kolossus.

Our heroes return to Siberia to free William from XANA's clutches, but first they must defeat the Kolossus and an army of robots. They better hurry too, because William's parents are visiting and his clone won't fool them for long.

In the ultimate battle against XANA, our heroes work with Franz Hopper to destroy the evil super computer forever. But first they must face everything XANA can throw at them, and Franz Hopper sacrifices himself to save the warriors.

With X.A.N.A. seemingly destroyed, the group must now shut down the super computer, but hesitates, giving Sissy the chance to find out all about the group's exploits. After using the "Return to the past" command one last time, the super computer is shut down. Note: This episode is basically a clip show with earlier events.