Jan 4, - The Grim Adventures of Billy and Mandy, Characters, Favorite Episodes, Favorite Characters, Villains. See more ideas about the grim, favorite. Mandy is one of the two title characters from The Grim Adventures of Billy is much shorter and she beats up Grim, Billy, and Irwin just for fun. Characters in The Grim Adventures of Billy & Mandy. Trending Pages. Mandy Grim Eris Nergal Billy Hoss Delgado Jeff the Spider Irwin. 1. Grim · 2. Billy · 3. Mandy · 4. Harold · 5. Hoss Delgado · 6. Jack O'Lantern · 7. Fred Fredburger · 8. Irwin.