Grim & Evil
Season 1, Episode 20: Big Trouble in Billy's Basement
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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 saying that they didn't want him there.
All Episodes - Season 1
Episode 1
Meet the Reaper
Episode 2
Skeletons in the Water Closet
Episode 3
Opposite Day
Episode 4
Look Alive!
Episode 5
Mortal Dilemma
Episode 6
Get Out of My Head!
Episode 7
Fiend Is Like Friend Without the
Episode 8
Grim or Gregory / Something Stupid This Way Comes
Episode 9
A Dumb Wish
Episode 10
Grim vs. Mom
Episode 11
Tastes Like Chicken
Episode 12
Grim or Gregory
Episode 13
Something Stupid This Way Comes
Episode 14
A Grim Surprise
Episode 15
Beasts and Barbarians
Episode 16
Hoss Delgado: Spectral Exterminator
Episode 17
To Eris Human
Episode 18
Billy's Growth Spurt
Episode 19
Billy and the Bully
Episode 20
Big Trouble in Billy's Basement
Episode 21
Tickle Me Mandy
Episode 22
Little Rock of Horrors
Episode 23
Dream a Little Dream