The Mountain Bug bears a slight resemblance to the Kankrelats in terms of its body shape, and its body is primarily silver in color. It also has a powerful set of cannons on the sides of its body that have two X.A.N.A. emblems, one on each cannon. It also sports two more X.A.N.A. emblems, one on the main body and the other on its face.
In the Game
The Mountain Bug was in charge of keeping a specific Mountain Replika in operation, and when Odd and Ulrich enter its chamber, the Mountain Bug attacks the two boys. After a grueling battle, the Mountain Bug is put out of commission, and the Replika is terminated.
The battle with the Mountain Bug consists of phases, each one resulting in the usefulness of Ulrich being compromised. Yumi and Aelita are absent from this boss fight, so either Ulrich or Odd are the only choices here, with Odd being much more preferable strategically.
The first phase involves the Mountain Bug firing its twin laser cannons in a scissor-like manner, essentially trapping the player in between its lasers. Thankfully, the player can jump over these. However, the Mountain Bug also has an attack where it slams its cannons on the ground in an attempt to crush the Lyoko Warriors. It has a hard time moving after it does this, so either of the two X.A.N.A. emblems on the cannons are quite vulnerable in this situation, leaving Odd and Ulrich to damage the X.A.N.A. emblems as much as they can. The emblems are also vulnerable when the Mountain Bug is attacking normally, so their is a chance someone like Odd may attack it.
After the two emblems on the cannons (and subsequently the cannons themselves) are destroyed, the second phase begins. This phase involves attacking the Mountain Bug's face, which now sports an Eye of X.A.N.A.. While Ulrich is still useful during this phase, Odd's abilities is increasingly emphasized, making him more a more logical character to use in this phase.
As soon as the final Eye of X.A.N.A. is exposed, the Mountain Bug goes berserk, making shockwave after shockwave and rendering any attempt to attack him physically useless, which in turn makes Ulrich's role in the battle finished. Odd is the only character who can defeat the Mountain Bug in this phase. Continue firing Lazer Arrows at the Mountain Bug's final Eye of X.A.N.A. to finally crush the Mountain Bug for good.
- Because of the strategy involved in fighting the Mountain Bug, the fanbase has affectionately referred to the fight as being exclusive to Odd.