Continuity mistake: Curly's shirt is stained with clay, yet he hasn't been hit in the chest yet.
Continuity mistake: When Minnie Mouse falls down on the pillow whilst attempting to skate, the pillow bursts and covers Mickey with feathers. When Mickey goes off skating you can see nothing surrounding the pillow, but when we return to Minnie later on, there are now a lot of feathers around it.
Other mistake: When the tortoise sees the hare sleeping, he goes right past him. There is some grass in the foreground at the bottom left, but the tortoise steps directly onto the grass, as if it were flat and in front of him. (00:03:28)
Continuity mistake: Before Beans the Cat puts the cat and dog into the piano, you can see there is an empty flower pot on the grass by the window. But when Oliver Owl sprays Beans with ink and he falls off the ladder, the flower pot has gone.