Dexter is a typical 8-year-old boy: other than the fact he's a genius with an enormous secret laboratory complete with computers, experiments and machines hidden beyond his bedroom wall. Despite sneaking to the lab when he can, he still can’t get away from his big sister, Dee Dee, who loves to dance her way into Dexter’s well-ordered world, disrupting his inventions and annoying him beyond belief
Because Dexter and Dee Dee can’t bring themselves to flush their beloved dead fish, Fishy, down the toilet, Fishy’s restless spirit haunts them. Soon other pet spirits from ‘The Sewer Beyond” rise from the dead and join fishy in haunting terror.
Dexter wants to find a golden diskette for a chance to tour Professor Hawk’s fabulous factory and win the mystery Grand Prize. Unfortunately, Dee Dee finds the diskette first but is nice enough to take Dexter as her guest.
Dee Dee keeps pelting Dexter with snowballs. Dad sees this and teaches his son the true art of snowball throwing. It turns out that Dad was the snowball king in his youth…until it all went terrible wrong.
Dexter wants to fit in with the neighborhood kids, but he doesn’t have an action figure. Dee Dee suggests that Dexter make his own action figure. Dexter’s figure is so great the other kids in the gang coerce him into making some for them.
In a parody of the classic Speed Racer, Dexter goes up against Mandark in the annual Soapbox Derby down the side of an erupting volcano. It looks like Mandark’s trickery until the mysterious Racer D enters the race out of nowhere.
When the whole family goes to a carnival, Dexter can’t get on a ride because he’s too short. Using scientific knowledge, he makes himself grow taller…and taller…and taller.
Using a nuclear reactor core, Dexter makes the perfect reading lamp. Dee Dee takes it so that she can play a game of hide and seek with Dexter, leaving him clues for him to follow. Dexter ends up having to find the core in an hour to avoid destroying the earth.
Dexter is desperately trying to avoid catching the flu as his family sneezes and coughs around him. He hides in his lab only to have the runny-nosed Dee Dee come in search of her pink hanky. Dexter puts himself into a bubble while De Dee destroys his laboratory.
Dexter finds that his normal scientific zeal is squelched on a day when everything that possibly can go wrong decides to do so. Dee Dee explains that his run of bad luck is due to the alignment of the moon and the Earth. So Dexter decides to move to the moon.
When Dexter gets a new bike, he’s told to go outside and play with his Rollerblading sister. Despite the fact that Dexter can’t ride, he gets embroiled in a race with Dee Dee.
Dee Dee befriends a white whale on a family outing to the beach. While Dee Dee is playing with this new friend, Captain Ahab and his evil whaling crew abduct Dee Dee. It is now up to the white whale and Dexter to save Dee Dee from the peril of the whalers.
When Dexter is harassed by two bullies and forced to go to the back if the school bus chasing his No. 2 writing implement, he must brave the legend of little Billy Blumberg, who disappeared back three years ago.
Krunk has been watching a Puppet Pals marathon on TV for four days straight. When he finally falls asleep, he dreams of joining them in their world.
It’s summer and De Dee goes off to space camp while Dexter must toil away on a farm where technology is forbidden. In an attempt to help, Dexter creates light from harnessing potato energy and is labeled a “bad see.” Luckily, Dexter is saved when Dee Dee drops out of the sky from a space capsule and is mistaken for the Magical Crop Fairy.
While vacationing in the woods with his family, Dexter finds Sasquatch tracks. He hopes to photograph the mythical beast, but Dee Dee finds the Sasquatch first. Having the same size feet, the two become close friends.
When Dee Dee takes pictures of his lab with her new camera, Dexter must stop the film from being developed. In true James Bond fashion, Dexter chases the film to a secret processing lab run by world criminals. He toils their plans but ultimately is too late to stop Mom from seeing the pictures.