The Grim Adventures of Billy and Mandy is an American animated television show that aired on Cartoon Network from 2001 to 2007. Originally doubled up with Evil Con Carne as Grim & Evil, the two shows broke off into separate series after two seasons, and Billy and Mandy proved to be far more popular. The show revolves around the titular children, who tricked the Grim Reaper into being their "best friend forever" and often have many adventures revolving around Grim's magical powers or the underworld whence he came from.
Four episodes of The Grim Adventures of Billy and Mandy, including the first episode of its first season as a separate show, revolve around a Harry Potter parody setting. These episodes involve Nigel Planter, a student at Toadblatt's School of Sorcery, and the various misadventures he gets himself into.
Episodes parodying Harry Potter
"Toadblatt's School of Sorcery"
The first episode to use the parody characters, "Toadblatt's School of Sorcery" begins with Billy and Mandy unwilling to attend the summer camps set up for them. Grim instead suggests they attend the summer school of Toadblatt's School of Sorcery, and set this up for them. When they arrive, Billy and Mandy, along with Nigel Planter, are sorted into the house of Weaselthorpe, which is stated to be much less popular than the other house, Gunderstank, which Grim is made Prefect of due to his prior friendship with the school's dean, Toadblatt. Due to Gunderstank continuously bullying and making fun of Weaselthorpe, Mandy makes plans to sabotage them, a plan Nigel immediately takes credit for despite having no part in making it. In the end, this backfires on him when the sabotage plan fails and he takes all the punishment for it.
Whilst out golfing, Grim, Billy, and Mandy run into Nigel Planter again, who is afraid to return to school and is hiding there from Lord Moldybutt, a wizard so evil merely speaking his name causes objects in the vicinity to break. However, he eventually agrees to return to school if Grim and company will go with him to protect him. The four encounter Moldybutt several times, each time being warned to stay away from the "Chamber Pot of Secrets" hidden in Dean Toadblatt's office. Eventually, they discover that the whole affair was actually a hoax by Toadblatt himself, who had dressed up as Moldybutt in an attempt to scare away Nigel, whom he detested.
"One Crazy Summoner"
When Billy's parents are attacked by an anaconda, the trio seek out the help of Nigel Planter, whom they believe to speak Parseltongue. However, when they get to Toadblatt's School and ask for his help, he reveals that he actually speaks Partialtongue, which allows him to snacks, not snakes. Furthermore, they find that mysteriously, despite Billy and Mandy being roughly the same age, Nigel and his friends have aged several years and he is now a young teenager. As Billy and Mandy are there, Nigel requests their assistance in wooing Huffefnie Pfefferpfeffer, an attractive girl he has a crush on. After determining that she has no interest in Nigel under normal circumstances, Mandy suggests using a Love Potion disguised in a box of chocolates. However, this plan backfires in the end, and Nigel accidentally eats one and falls in love with the box of chocolates itself.
In this finale of Nigel Planter's saga, Billy and Mandy visit a joke shop and once again run into Nigel, who has once again aged and is now a young adult. He reveals his magic, always subpar at best, recently diminished even further and he was subsequently kicked out of Toadblatt's School. He ends up stealing Grim's magical scythe and intends on using it to return to the school and get his revenge on Toadblatt and the others who made fun of him. Meanwhile, Lord Moldybutt has returned for real this time, and is looking for Nigel. He meets up with Grim, Billy, and Mandy, and enlists their help to find Nigel. At the episode's end, Grim is able to recover his scythe before any lasting harm is done, and Moldybutt reveals the real reason he was after Nigel. It turns out that Nigel was never a wizard at all, but was actually the non-magical heir to a large peanut-making company, and that Moldybutt was a lawyer attempting to give Nigel his rightful fortune.
Elements from the Nigel Planter episodes also appear in the video game based off the series. Two of the game's stages come from these episodes. The first, Coliseum of Chaos, is based off the coliseum that Nigel is sent into for punishment at the end of "Toadblatt's School of Sorcery". Dean Toadblatt sits in the middle of this level's stands, and will turn any combatants that come near him into frogs. This level also serves as the stage for the game's tutorial. The second stage, Warlockery and Sorcerizing, is set in Toadblatt's office. After a certain period of time, a meteor shower will hit the stage and destroy most of the office's outer walls, and after more time has passed, Toadblatt, who was sleeping at his desk near the stage's center, will wake up and shrink everyone down onto his desk.