When Billy Dilley's science fair project the Cheeserator gets struck by lightning and goes haywire, Billy, his lab partners Zeke and Marsha, and his pet rat Anaximander, find themselves stuck in a strange underground land called Subterranea-Tania.

On their second day in Subterranea-Tania, Billy, Zeke, and Marsha find their way back to the Cheeserator after getting kidnapped by a vicious Pterosaur. After getting back to the Cheeserator, the trio builds a house made out of extra parts for safety.

Zeke, the King of Calzones, must defend his title when a rival chef enters the picture.

Billy invents the grafting machine and adds creature parts to his body.

Billy and Zeke help Marsha find romance, but an unexpected guest could ruin everything.

Billy and Zeke have an epic sports showdown with the neighbouring Troggies.

Billy repeatedly tries to steal Marsha's diary. Billy is excited to meet Count Wretcher, an eccentric neighbour and fellow inventor.

Billy strikes up a friendship with the sludge-obsessed Count Wretcher, who offers to help fix the Cheeserator for his own nefarious plans.

Billy meets a new friend and a new romantic interest on the same day and is forced to choose between the two.

When Billy becomes the new apprentice to Subterranea-Tania's resident sorceress Hag Witch, the two concoct a love potion to try on Count Wretcher.

Billy takes extreme measures when Marsha convinces him he has brought a curse upon himself.

Billy invites a heroic warrior named Zartran to stay at his house.

Billy and Zeke try to figure out Marsha's unexplained bout of klutziness.

Zeke is blown away when he meets his favorite extreme sports hero, Tommy X.

Zartran convinces Billy to pretend to be the nephew of an old lady to scam her out of her secret treasure.

Billy is jealous of his new friend's wart.

Teased by a gang of lizard youths for his hair, Billy decides to save up for a wig by looking after Big Doug's prized mammoth.

Billy, Tony and Yucky guard Hag Witch's house while she's out, but they can't resist breaking into her spells cabinet.

Tired of being castle-bound by his domineering mother, Count Wretcher breaks loose and tries to convince Billy and friends to continue fixing the Cheeserator.

Billy grows jealous when Zeke and Marsha befriend a strange creature called Jared, who eventually turns out to be a hideous flesh-eater who suffered from amnesia.

Feeling ignored by Anaximander, Billy decides to take in a new pet, a slug called Sluggy.

When Zeke starts avoiding his chores by throwing his trash on the roof, he and Billy end up dealing with a large-scale garbage problem on their hands.

When the Gorks' sacred slime is tampered with, Billy is enlisted to help find the culprit.

When Anaximander starts molting his fur, the people of Subterranea-Tania decide to put on a show to make him feel better.

As Billy, Zeke and Marsha prepare to leave Subterranea-Tania by throwing a "farewell party", Billy accidentally causes a robot-alien invasion led by an evil clone of Billy. The people of Subterranea-Tania then turn against Billy and it's up to the trio to try to stop the invasion once and for all.