Franz Hopper was the creator of Lyoko, X.A.N.A., and the father of Aelita. He created Lyoko, and X.A.N.A. to be the staging grounds and means of the destruction of Project Carthage, a secret government program he created to intercept enemy communications. By the time he was nearing the end of his completion of Lyoko, he became very paranoid and insane to some degree. He repeated the same day over 2000 times using the Time Reversion feature of the supercomputer to accomplish his goals. At the last moments, he and Aelita fled to Lyoko, only to be attacked by X.A.N.A. and his monsters. Franz was captured and taken to an unknown location within Lyoko. He escaped, however, and sacrificed himself for his daughter in The Key. The Lyoko Warriors continued to search for him after that. Aelita found a fragment of Franz's DNA in Carthage, so she still hoped. In Final Round, Jeremie and Aelita finally managed to track him down in Lyoko's code, but Lyoko was destroyed by X.A.N.A. before he could be materialized. However, it seems that he escaped to the Internet because he sent a coded message to Team Lyoko from there after Lyoko was destroyed.
He loved playing the piano, as seen in the various visions and the memory sequence that Aelita has. He also had a wife, who mysteriously disappeared.
In Wrong Exposure, it is revealed that Franz's real name is Waldo Schaeffer. Hopper is the last name of Aelita's mother, and Franz is his middle name. Franz changed his name when he and Aelita moved to Hermitage since he wanted Aelita and himself to have a fresh start. He was once a science teacher at Kadic but was replaced by Suzanne Hertz after his disappearance 9 years prior to the show. He ultimately sacrificed himself to destroy X.A.N.A. once and for all by covering Aelita from the Mantas' laser blasts after she had been hit once while she finished activating the multi-agent program. For more information, see Wrong Exposure.
- One real computer scientist was called "Hopper",  but writers stated it is a coincidence.
- His only apperence was in the shape of a orb to save Aelita, but also has a health bar like everybody else.
- Aelita made a reference that Hopper was a threat to X.A.N.A., this is not true in the first & second seasons but in the third, this is true.