Susan prefers the name Mandark as he hates his birth name. Its humiliating. Mandark appears to be smarter and his inventions far more advanced in comparison to Dexter when he first appears in the series. While Dexters lab had a steriotypical "squared" design, Mandark's lab was spherical in shape. Mandarks superiority was shown by his ability to read minds (using technology). After a series of attempts by Dexter to prove his power and intelligence, Mandark forces Dexter to close down the lab, because it was using power that Mandark could use to enhance his own lab. However, eventually Dexter tricks Dee-Dee into leveling his lab for him.
Mandark begins to love Dee-Dee despite being constantly hindered by her.