A mysterious thief has stolen the prosperous Happy Valley's most prized possession: the musical Singing Harp. Can Mickey, Donald, and Goofy find the answer in the irritable Willie the Giant's magnificent castle up in the blue sky?
| Actor | Role |
|---|---|
 Walt DisneyMickey Mouse (voice) | Mickey Mouse (voice) |
 Clarence NashDonald Duck (voice) | Donald Duck (voice) |
 Pinto ColvigGoofy (voice) | Goofy (voice) |
 Sterling HollowayNarrator (voice) | Narrator (voice) |
 Paul FreesLudwig Von Drake (voice) (uncredited) | Ludwig Von Drake (voice) (uncredited) |
 Billy GilbertWillie the Giant (voice) (uncredited) | Willie the Giant (voice) (uncredited) |
| AAnita GordonSinging Harp (voice) (uncredited) | Singing Harp (voice) (uncredited) |