After a high school lab experiment goes horribly wrong, Mordecai and Rigby must go back in time to battle an evil volleyball coach in order to save the universe — and their friendship.
| Actor | Role |
|---|---|
 J.G. QuintelMordecai / Hi-Five Ghost (voice) | Mordecai / Hi-Five Ghost (voice) |
 William SalyersRigby (voice) | Rigby (voice) |
 Sam MarinBenson / Pops / Muscle Man (voice) | Benson / Pops / Muscle Man (voice) |
 Mark HamillSkips (voice) | Skips (voice) |
 Minty LewisEileen (voice) | Eileen (voice) |
 Jason MantzoukasMr. Ross (voice) | Mr. Ross (voice) |
 David KoechnerPrincipal Dean (voice) | Principal Dean (voice) |
 Roger Craig SmithJablonski / Frank Smith / Fast Food Guy (voice) | Jablonski / Frank Smith / Fast Food Guy (voice) |
 Ali HillisShip Computer / Rigby's Mom (voice) | Ship Computer / Rigby's Mom (voice) |
 Kurtwood SmithGene (voice) | Gene (voice) |
 Eddie PepitoneSherm (voice) | Sherm (voice) |
 Paul F. TompkinsGino (voice) | Gino (voice) |
 Fred TatascioreFather Time / Security Guard / Additional Voices (voice) | Father Time / Security Guard / Additional Voices (voice) |
 Steve BlumTechmo / Brit / Commander / TV Game (voice) | Techmo / Brit / Commander / TV Game (voice) |
 Janie Haddad TompkinsMargaret (voice) | Margaret (voice) |