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Code Lyoko Wiki

The fourth season of Code Lyoko originally aired from May 18, 2007 to November 17, 2007. It mainly focused on the group traveling the Internet in search of X.A.N.A., in their virtual submarine: the Skidbladnir. Using their ship, they go searching for Replikas to destroy them to prevent X.A.N.A. from succeeding in world domination. They also try to rescue a X.A.N.A.-fied William and bring him back home.


Recreating Lyoko and the Return of William

William returns as X.A.N.A.'s loyal minion

After the Core of Lyoko is destroyed, the group searches for a way to rebuild Lyoko once more so they can travel through the web. After a long summer, Jeremie and Aelita announce that they have successfully rebuilt Sector Five. The group also discusses William and how he was lost in the Digital Sea after Lyoko was destroyed. However, Jeremie has a trick up his sleeve and calls the principal to inform him that William would not be returning to Kadic Academy anytime soon. However, to add to the mystery, William unexplainably returns. This was simply a plot by X.A.N.A. to capture and kill Aelita. After a brief battle, the group discovers that William is permanently X.A.N.A.-fied and they must rescue him. (William Returns)

The Skidbladnir

The Skidbladnir in the middle being fully constructed.

Since X.A.N.A. is now scattered around the internet, the team is now facing to how to directly counter X.A.N.A. As Jeremie works around the clock to find a solution, he finally comes up with the idea of a virtual submarine, named the "Skidbladnir". X.A.N.A. attempts to destroy the ship before it is fully completed, but fails while trying ao. However, he is able to steal some data which would be later used to program William's own mini-submarine called Rorkal. (Skidbladnir)

Battle of the Replikas

The Lyoko Warriors discover the Forest Replika.

With the Skidbladnir all programmed and ready to go, the Team decides to hunt down X.A.N.A. on the network as to bring William and Waldo Schaeffer home. During the maiden voyage, the team stumbles upon an an unknown sphere. However, the team later realizes that this was not in fact Lyoko. (Maiden Voyage)

They later return to this mysterious sphere and realize it is an exact copy of Lyoko, except that instead of housing four sectors, it houses just one. (Replika)

These "Replikas" are housed the same way as Lyoko is: inside a supercomputer. After this discovery, Jeremie finds a way to bring them to the real world as spectres to destroy supercomputers that house the Replikas. (Lab Rat, Bragging Rights, A Lack of Goodwill, Hard Luck, A Space Oddity, Cousins Once Removed, Cold Sweat, Down to Earth)

Return of Franz Hopper

Franz Hopper.

Waldo Schaeffer (also known as Franz Hopper) makes his first re-appearance after Aelita is thrown into the Digital Sea. He saves Aelita, and also provides Jeremie with some data before disappearing once again. (Distant Memory)

Schaeffer appears for the last time in the penultimate-episode. He provides Jeremie with data that could potentially destroy X.A.N.A. (Fight to the Finish)

Demise of Franz Hopper and the Annihilation of X.A.N.A.

The Multi-Agent program in a working state.

With the data finally accessible, Jeremie programs the "Multi-Agent Program" which can destroy all of the Replikas and X.A.N.A. himself. However, there was not enough power available. As Mantas were attacking Franz Hopper, he offered the power to utilize the program.

Just as the program began to run, he was permanently devirtualized. X.A.N.A. was wiped out along with the Replikas, with the cost of Waldo's own life as well. (Fight to the Finish)

List of Episodes

Ep No. Pro No. Name Image French Title Airdates
1 (66) 401 William Returns
66 william returns.png
Renaissance US: May 18th, 2007
FR: August 13th, 2007
2 (67) 402 Double Take
67 double take.png
Mauvaise réplique US: June 12th, 2007
FR: August 14th, 2007
3 (68) 403 Opening Act
68 opening act.png
Première partie US: June 19th, 2007
FR: October 29th, 2007
4 (69) 404 Wreck Room
69 wreck room.png
Double foyer US: June 26th, 2007
FR: August 15th, 2007
5 (70) 405 Skidbladnir
70 skidbladnir.png
Skidbladnir US: July 3rd, 2007
FR: August 16th, 2007
6 (71) 406 Maiden Voyage
71 maiden voyage.png
Premier voyage US: July 10th, 2007
FR: August 17th, 2007
7 (72) 407 Crash Course
72 crash course cut.png
Leçon de choses US: July 17th, 2007
FR: August 20th, 2007
8 (73) 408 Replika
73 replika.png
Réplika US: July 24th, 2007
FR: August 21st, 2007
9 (74) 409 I'd Rather Not Talk About It
74 I'd rather not talk about it.png
Je préfère ne pas en parler US: July 31st, 2007
FR: August 22nd, 2007
10 (75) 410 Hot Shower
75 hot shower.png
Corps céleste US: August 23rd, 2007
FR: August 14th, 2007
11 (76) 411 The Lake
76 the lake.png
Le lac US: August 21st, 2007
FR: August 24th, 2007
12 (77) 412 Lost at Sea
77 lost at sea.png
Torpilles virtuelles US: August 28th, 2007
FR: August 27th, 2007
13 (78) 413 Lab Rat
78 lab rat (experience in french).png
Expérience US: Unaired (Aired Online)
FR: August 28th, 2007
14 (79) 414 Bragging Rights
79 bragging rights.png
Arachnophobie US: September 8th, 2007
FR: August 28th, 2007
15 (80) 415 Dog Day Afternoon
80 dog day afternoon.png
Kiwodd US: September 15th, 2007
FR: August 29th, 2007
16 (81) 416 A Lack of Goodwill
A Lack Of Goodwill Title.jpg
Œil pour œil US: September 22nd, 2007
FR: August 30th, 2007
17 (82) 417 Distant Memory
82 distant memory.png
Mémoire blanche US: September 29th, 2007
FR: August 31st, 2007
18 (83) 418 Hard Luck
83 hard luck.png
Superstition US: October 6th, 2007
FR: September 8th, 2007
19 (84) 419 Guided Missile
84 guided missile.png
Missile guidé US: October 13th, 2007
FR: September 15th, 2007
20 (85) 420 Kadic Bombshell
85 kadic bombshell.png
La belle de Kadic US: November 3rd, 2007
FR: September 22nd, 2007
21 (86) 421 Canine Conundrum
86 canine conundrum.png
Kiwi superstar US: November 10th, 2007
FR: September 29th, 2007
22 (87) 422 A Space Oddity
87 a space oddity.png
Planète bleue US: November 17th, 2007
FR: October 6th, 2007
23 (88) 423 Cousins Once Removed
88 cousins once removed.png
Cousins ennemis US: November 17th, 2007
FR: October 13th, 2007
24 (89) 424 Music to Soothe the Savage Beast
89 music to soothe the savage beast.png
Il est sensé d'être insensé US: Unaired (Aired Online)
FR: October 20th, 2007
25 (90) 425 Wrong Exposure
90 wrong exposure.png
Médusée US: Unaired (Aired Online)
FR: October 27th, 2007
26 (91) 426 Bad Connection
91 bad connection.png
Mauvaises ondes US: Unaired (Aired Online)
FR: November 3rd, 2007
27 (92) 427 Cold Sweat
92 cold sweat.png
Sueurs froides US: Unaired (Aired Online)
FR: November 3rd, 2007
28 (93) 428 Down to Earth
93 down to earth.png
Retour US: Unaired (Aired Online)
FR: November 3rd, 2007
29 (94) 429 Fight to the Finish
94 fight to the finish.png
Contre-attaque US: Unaired (Aired Online)
FR: November 10th, 2007
30 (95) 430 Echoes
95 echoes.png
Souvenirs US: Unaired (Aired Online)
FR: November 10th, 2007


  • This is the longest season produced, boasting thirty episodes rather than twenty-six.
  • Yumi, Aelita, Odd and Ulrich don new attire on Lyoko, which debuts in the season's second episode Double Take. Almost every character gets new attire on Earth as well, which first appears in Maiden Voyage and is seen in every episode after (except for The Lake).