Grim & Evil

After having a nervous breakdown and leaving the house in the first episode, Billy's mother, Gladys, returns. She meets Grim again and, this time, she plans to destroy him once and for all. When Grim goes to the kitchen for a glass of water, Gladys attacks him and shatters his skeleton. In the end, Grim assures the kids that Gladys has won the battle but not the war.

Dr. Ghastly discovers that Hector's face may still be intact and sends out a search party to get it. This episode also reveals how Dr. Ghastly and Hector met, as well as how Hector was defeated by Cod Commando in the first place.

With Irwin not answering the phone, Billy's parents missing and Mandy saying she wants "Billy for dinner", Billy and Grim assume Mandy is a cannibal who ate Billy's parents and friends. Looking for proof, Billy and Grim find tiki figures and arrangements for a celebration in Mandy's backyard. Ultimately, it is revealed that they are just celebrating Billy's birthday. Still, Mandy burps out Irwin's glasses, revealing that Mandy ate Irwin as Billy screams in terror.

It's Halloween, Billy, Mandy and Grim go trick-or-treating. Grim mistakes a woman for Atrocia, the host of the all-night Halloween marathon on TV and goes to talk to her. Upon looking at her face, Grim realizes his mistake; however, the woman mistakes Grim for her son, Gregory, and takes him home Gregory is now Grim, and does not have a stomach. At the same time, Billy mistakes Gregory for Grim and he and Mandy take him with them. In the end, Billy and Mandy take Gregory back to his mother and Grim goes back with them.

Skarr is evesdropping on Hector and Dr. Ghastly about their new secret weapon—a disenigration gun. Too their dismay Estroy comes up with a better version of the gun. He also surprises them by inviting them to dinner. Hector accepts as a way to steal some of his ideas. Hector and Ghastly arrive at Estroy's neighboring island while Skarr slips around the back. Of course he falls while scaling the wall and lands in a pond of electric eels. At dinner, Estroy tries to recruit Dr. Ghastly. In the meantime, Skarr has gotten into the building and he reaches the secret plans. Estroy reveals that his intentions were to make Dr. Ghastly his new assistant. She's reluctant to the idea and they leave in a huff. Back at home, Skarr reveals the plans to them and they immediately begin construction.

Nergal, the fiend from the center of the Earth, returns to the surface, emerging a carnival with him, trying once more to make friends. In the following, Billy tries to help Nergal make friends by being considerate, but Nergal fails to apply correctly his advice. When Nergal is told that Grim was forced to be Billy and Mandy's friend-slave, Nergal then decides to force the world to be his friends by turning them into dark beings similar to him. In the end, Nergal turns Billy, Mandy, Grim and even the viewer (thus breaking the fourth wall) into one before the episode ends.

Billy tells Grim to help him throw a surprise birthday party for Mandy. Then, a reluctant Grim helps Billy prepare a cake while keeping it a secret from Mandy. In the end, a somewhat surprised Mandy reveals that her birthday isn't here for the next five months, something that Billy already knew about.

Con Carne takes over a Mister Rogers-type children's show in an attempt to rule the world by first winning over the children.

Billy and Irwin have been playing their favorite video game, Beasts and Barbarians, for three days non-stop. In an attempt to stop their video game addiction, Grim transports them all to a real-life version of the game. Seeing as Billy and Irwin are still doing good in their quest, Grim increases the difficulty by manipulating the traps himself. In the end, Billy, Mandy, and Grim return home escaping from a giant cyclops, while Irwin remains trapped.

Billy, Mandy, and Grim go to the museum on a school trip. There, they meet Hoss Delgado, self-appointed hunter of the paranormal, who upon spotting Grim, tries to eliminate him. Subsequently, Grim and Delgado engage in a fight. Finally, Delgado quits hunting Grim when he realizes Billy and Mandy control him. In the end, Delgado continues his own adventures and is seen fighting a werewolf.

General Skarr turns Con Carne in to the FBI when he finds out that Con Carne is "the World's 23rd Most Wanted" criminal with a large cash bounty on his head. When it turns out no lawyer on earth will defend Con Carne, he finds himself in court defended by Major Doctor Ghastly – and prosecuted by the Cod Commando.

While going to the shopping mall with Billy and Mandy, Grim spots the beautiful Eris, the goddess of discord and chaos, and tries to ask her out. However, Eris is not interested in the skinless Grim, but in the muscular Adonis. Then, Eris invites Mandy to join her in creating chaos using the Apple of Discord. Although initially they get along, Eris pulls a prank on Mandy, who subsequently tries to get revenge. In the end, Mandy fools Eris into thinking that Adonis is in the movie theater and Eris accidentally kisses Grim.

Billy eats too much junk food that makes him feel sick. Grim prepares him a remedy using his granny's recipe, but this medicine makes a parasite to start growing in Billy's back, which Billy names Yap-yap. In the following, Billy and Yap-yap continue eating junk food, so Mandy suggest to use the antidote to the original remedy. Eventually, Yap-yap, now looking like a smaller version of Billy, detaches himself from Billy (which would have technically cured Billy without the need of him drinking the anitdote), and tries to escape from the antidote. In the end, Yap-yap drinks the antidote and is destroyed.

Major Doctor Ghastly invents the Temporal Confabulationater Izationizer Unit – a time machine that works so well that Ghastly, Hector and Skarr end up meeting their future selves and Destructicus Con Carne, son of Ghastly and Hector, as both an infant and an adult.

Billy is constantly provoked by a bully named Sperg and runs over to Grim for help.

After taking the Underworld's "Bad Book" from Grim, Billy becomes possessed by an evil presence. Then, Billy steals Grim's scythe, and uses it to open a portal to summon Yog-Sothoth. In consequence, Mandy calls for Hoss Delgado to battle Billy. It is revealed that the portal can only be sealed by throwing the book into it. As Billy eats the book, Mandy throws Billy himself into the portal, restoring everything to normal. Instants later, a portal opens up and Billy comes out and says they didn't want him there.

Rupert the Green-Nosed Reindeer saves Christmas when Hector Con Carne tries to ruin it.

Mandy and her parents leave the city for a day, which makes Billy feel lonely. Then, Grim uses his supernatural powers to create a fake Mandy with pieces of dolls and toys for Billy to play with. However, the "new" Mandy is too aggressive with Billy, and he starts fearing her. The next day, the real Mandy returns home, and promptly destroys the new Mandy while in the see-saw.

In this musical episode, which pays homage to Little Shop of Horrors, Billy befriends a singing brain-eating meteor (voiced by Voltaire) that falls from the sky after when everyone doesn't want to play with him because they are busy. With Billy's help, the creature grows bigger and eventually eats the brains of all people in Endsville (turning them into zombies with glowing green eyes). The last brain he eats is Mandy's, which results in the creature transforming into a pink, brain-eating Mandy meteor.

This is a mini musical. At first, Hector is singing about some of the things he adores. This leads into why he should take over the world (classical). This goes into Dr. Ghastly singing about her scientific work, leading into her baking pies for science (rock opera). The pies are sent to all the people who are singing about the temptation of pies in the sky. Skarr breaks in with a solo about hitting people with pies. Even Boskov gets a solo (rock opera). Meanwhile, the organization that's here to stop Evil is out of commission from too much pie; as are all the citizens. This leads back into Hector rejoicing in song about his success with the pie scheme until Cod Commando infiltrates the "pie in the sky" with a patriotic tune. In the end, no one could fight any one any more because they have had "too much pie".

Billy, Mandy and Grim eat moldy pizza leftovers and after falling asleep, they have nightmares. Billy dreams of cute bunnies which turn into horrific and deadly monsters; Grim dreams of an endless number of bossy Mandys; Mandy dreams of being pulled into a volcano and then commanding demons at the rhythm of music, in a scene that reminisces the Night on Bald Mountain segment of Fantasia. In the end, Mandy reveals that her dream was actually very pleasant and she eats the last slice of the rotten pizza.