Continuity mistake: When the ants have Donald's hat, they throw it over the edge of the cliff. When we see Donald in the river in the next shot, there is no sign of the hat.
Continuity mistake: When the ant jumps into the anthill with an olive, the style of the anthill changes between shots.
Continuity mistake: After Donald has planted the dynamite in the anthill, he stops at an area and puts his fingers in his ears. At this point you can see there is nothing surrounding him, but when the dynamite explodes, there are now some small bushes and rocks around Donald.