While Dexter with Gumball was breaking inside Mandark's lab, Dr. X had a discussion with Sebastian Longquin about Mandark. Dr. X explained Sebastian Longquin the past of Mandark that he was grown up with hippie parents but self liked science much more. Dexter became his archrival since he always made fun out of him. After he had killed Dee Dee he went into a depression until Bell came to him to take him with her and get a better life. Dr. X raised Mandark like he was his own son and Bell saw him as her big brother.