Susan Astronominov (born September 9, 1983), or commonly known as Mandark, Dexter's arch-nemesis. Approximately equal in intelligence to Dexter, he too possesses his own laboratory, which has a very red-and-black color scheme (although it was a normal shaped, brightly lit building before it was rebuilt) and may be organic-based. It also is sphere shaped, opposing the design of Dexter's Laboratory. In his original appearance, his technology and knowledge far exceeded even Dexter's, and he ordered Dexter to shut his laboratory down, since it was taking away valuable power from Mandark's. However, after Dexter tricked Dee Dee into making Mandark's lab equal to the ground, he has been forced into playing catch-up with Dexter, being an eternally one-step-behind rival. In spite of her role in his setbacks, Mandark has a crush on Dee Dee, who initially resented the attention, but developed an easier relationship with him in the later series. He was originally referred to as "Mandark" though his true name was revealed to be "Susan" (a reference to A Boy Named Sue) after becoming a recurring character - a name which humiliated him in his early phases in life and a case of horrible parenting. In one episode called Dee Dee's Rival, it is revealed that he has a sister named Olga Astronominov, also called Lalavava, who seems to have total control over him, although she hasn't been seen or heard of since. After season 2 ended, he seems to have built a new laboratory with a more dark, evil look, topped off with a red glow. Though, during his first appearance, Dexter is thought to have seen Mandark for the first time, it is revealed in one episode that Mandark first met Dexter when he was making fun of the former's real name, and this encounter triggered Mandark's hatred of Dexter. It can also be assumed that it caused Mandark to become evil, as he appears to be simple and peace-loving before the encounter, a sharp contrast to his then-hidden, evil personality later on. His parents are stereotypical hippies, who despise his "evil techno-gadgets", and always call him by Susan, which makes him extremely angry.
Mandark serving as one of the Org's Scientist that created twisted and possibly awkward arsenal.
he also led some of the Orgs member to attack the Safe house to kidnap the Ultimawhip wielder, Sadie.