Revealing mistake: When Oliver is holding the drunk, he says "We'll have it in just a jiffy." Arthur Housman (The Drunk) then repeats the line, and you can see Oliver Hardy mouthing the line as well.
Revealing mistake: When Stan falls off the balcony and into the fountain when throwing Oliver's bowler hat back at him, you can see water marks on the walls caused by splashes from previous takes.
Revealing mistake: Ollie throws a flower pot at Stan. Stan ducks and the pot continues through the house, breaking a window and hitting a gardener outside. On the DVD of the film, the long wire the flower pot is attached to is visible.