Best comedy movie mistakes of 1931
Continuity mistake: When Stan pulls the door into Oliver's face, Oliver falls backwards and the spring on his back sends him skywards and onto the piano. When Oliver falls onto the piano, you can see that there is nothing on his stomach, but a few seconds later he is covered with piano hammers and other parts from the interior of a real piano.
Continuity mistake: The second-story room of the prison warden's daughter is on fire and she is screaming for help. Stan has trouble connecting a fire hose to a water valve and Ollie winds up completely drenched, but in all the following scenes where Ollie is using a ladder to try to rescue the woman, his clothes are dry.