Greg Eagles as Grim / Sperg (voice)

Richard Steven Horvitz as Billy / Billy's Dad (voice)

Grey DeLisle as Mandy (voice)

Vanessa Marshall as Irwin (voice)

Kari Wahlgren as Velma Green the Spider Queen (voice)

Maxwell Atoms as Jeff the Spider (voice)

Dee Bradley Baker as Chocolate Cow (voice)

Jennifer Hale as Gladysaur (voice)

Chris Cox as Principal Goodvibes (voice)

Jane Carr as Pud'n (voice)

Henry Gibson as Lord Pain (voice)

Phil LaMarr as Mr. Spleen (voice)

Rachael MacFarlane as Mindy / Velma's Mom / Eris (voice)

Michael McKean as Kalgoron (voice)

Renee Raudman as Ms. Butterbean (voice)

David L. Lander as Curtis (voice)

Fred Willard as Boogey (voice)

James Sie as Plain Cow (voice)

Armin Shimerman as General Skarr (voice)

Dave Wittenberg as Velma's Dad / Spider #1 (voice)