Mortlegax loves being evil and tries hard to act like it. He appears to be strict but also very fair and willing give others a chance. Mortlegax takes evil very seriously and always has to see details. He loves his evil laugh, complete with background thunder and lightning.
Role in the series
Mortlegax is first seen complementing Jumba on his experiment work via computer screen. At first, Jumba is pleased, but then Mortlegax reveals they've been getting reports of Jumba's experiments not acting evil. He says they can't risk the scandal if Jumba has gone good, so he will have to revoke his membership. Jumba tries to get him to reconsider, but Mortlegax refuses. Lilo then intervenes by standing up for Jumba, and Mortlegax assumes that she is his evil assistant, but Lilo points out that it's actually Stitch. Mortlegax says that he is in Jumba's quadrant next Tuesday visiting his Aunt Bootsie and offers a deal. If Jumba can convince him personally that he is still evil, he will extend Jumba's membership, and Lilo agrees to his deal.
When Mortlegax arrives at the Pelekai residence, Lilo and Stitch try to trick him into thinking that Jumba was still evil by showcasing several of his evil experiments on the Internet. Lilo and Stitch's facade is successful at first until Mortlegax notices a screen of Experiment 262 (Ace) rescuing a neighbor's cat from a house that was on fire. As a result, Mortlegax revokes Jumba's membership and promptly leaves.