After getting ready to go to bed, the boys drop the candle a few times, and it seemingly goes out. When they pick it up, it is lit again without them lighting it.
Stan is standing in the hall of Laurel Mansion with wet patches on his jacket from the rain outside, but when he goes upstairs, he's dry.
The fishing line yanks the hat off Ollie's head twice between shots.
Stan crumples up the newspaper he's been reading and throws it in river, but the wind blows it back as a full-open paper into Ollie's face.
When the boys are attacked by the "Housekeeper", the killer's knife hits the table and bends, showing it is obviously made of rubber.
At the mansion, when lightning his seen, the sound of the electrical arcing causing the effect can be clearly heard numerous times.