Dr. Gevaarlijk is a professor of evil science from . She is very short with blond hair and wears glasses. She was a teacher of Dr. when he took Evil Science 101. She hated and tormented him when he was her student.
Doofenshmirtz wrote her a letter inviting her to Danville to impress her with the enormity of his evil schemes. He tried to show off his inventions and his nemesis, . Also in honor of her visit, he planned to blow up the moon with an unnamed laser device to stop all songs about it. She approves of this plan since she, too, despises moon-related songs. Unfortunately, the plan backfires when he leans on the laser and redirects it towards a nearby dam. Because she enjoys a good toe-tapping dam song, she is even less impressed with Doofenshmirtz's schemes.
In the end, she tells Doofenshmirtz that evil doesn't always have to be on a large scale. He could just spread evil in the little things he does everyday, but that he can't even do that.