When Billy and Irwin start making prank calls, everybody knows that Billy is behind the calls because every telephone has a caller ID. Then, while Billy searches in Grim's trunk in the basement for something to defeat the caller ID, he finds a skull-shaped phone with no caller ID. Then, Grim warns him to not use the phone, because it is used to call the ancient demon Cthulu, whose sole appearance makes people go mad, and if awakened will cause the destruction of the world. Despite Grim's warning, Billy and Irwin use the phone anyway, and they are sucked into it by tentacles. After the commotion, Mandy and Grim go search for Billy, and they find themselves in a strange place with several other tentacled creatures. In this place, Billy and Irwin have been hired as official prank callers and steadily turn into tentacled monsters. However, their pranks actually make the people answering the phone to become monsters, so Mandy decides to confront Cthulu himself to put an end to this. In the end, Mandy tricks Cthulu into answering her cellphone, and when he is sucked into it, Mandy disconnects the call, trapping Cthulu in the telephone lines forever. However, just as Billy, Mandy, and Irwin are about to leave, Grim has destroyed the phone at the basement, and they are unable to return.