Continuity mistake: When Donald Duck is holding on to Mickey Mouse when Goofy is dangling on the ladder, you can see there is a window underneath Donald, but when he has his feathers burned in the next shot, the window has disappeared.
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.
Continuity mistake: When Mickey Mouse is preparing to start the concert, you can see that he has a music book on the stand in front of him. When the band start playing in the next shot, the book has disappeared, and in the shot after that, it is back again.