Franz

From Code Lyoko Wiki

Franz Hopper is the creator of Lyoko. He is also the father of Aelita. He can play the piano, and taught Aelita when she was a little girl. Fraz Hopper left behind his diary, which Jeremie soon decoded, and found out how he created lyoko. The gang thought he was a bit insane, toward the end, as it says in The key. Aelita hated him at first, but when she learned how sacrificed himself to restore her memories, she grew to love him.