Big Trouble in Billy's Basement The Grim Adventures of Billy & Mandy : Season 1 Episode 20
TV-Y7-FV Cartoon Network 30m int(0)
Aired: October 4th, 2002 @ 8:30 PM EST on Cartoon Network
After taking the Underworld's "Bad Book" from Grim, Billy becomes possessed by an evil entity. 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.