Continuity mistake: When the seven dwarves run scared down the stairs and out of the door, Dopey pulls the handle of the door from the inside until it breaks out and falls away. The next scene when the dwarf opens the door, the handle is there again. (00:33:00)
Continuity mistake: During the locust invasion, two of Paul Muni's men collapse and are covered in locusts. Muni picks them up, but suddenly, all of the locusts have disappeared.
Revealing mistake: When the piano lid smashes Cary Grant's fingers, the lid obviously stops inches above his hand, even though a drink is positioned on the piano in an attempt to hide the gap.