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.
Continuity mistake: Before Little Kitty attempts to recite "Mary Had a Little Lamb", you can see there is writing on the blackboard behind her. When she makes her exit, the writing has disappeared, and when Ham and Ex appear, the writing is back again.