Dexter finds a lost Labrador Retriever, but when he teaches the dog to speak human language, he turns out to be very annoying, prompting Dexter to find the dog’s owner.

Dee Dee builds a tree house and allows everyone inside except Dexter, in revenge for the times he kicked her out of his lab.

Dexter’s parents and Dee Dee have their minds taken over by an alien life form that escaped from Dexter’s lab.

Dexter has a crush on his teenage babysitter Lisa (Kath Soucie). When he finds out that she has a boyfriend, he sabotages their relationship and accelerates his age by ten years in an attempt to win her heart.

Dee Dee’s father trains her to fight a gang of bicycle-riding rogues dressed as ninjas who target her paper route every morning.

Mandark’s birth and origins as the child of hippies are revealed, as is the beginning of his rivalry with Dexter and the cause of his villainy.