In the shot of Echo (from behind) reading the newspaper, the headline is on top. In the immediate reversal shot of him from the front, the headline is at the bottom of the folded newspaper, but he hasn't flipped the paper to that position.
The Ape at the pet store is clearly a chimpanzee, but it is depicted as larger than a real chimpanzee can grow.
Toward the end of the film, while Echo (Lon Chaney) and Rosie (Mae Busch) are having their conversation in the wooded area outside the cabin, both characters are casting shadows on the scenery behind them, revealing that the 'woods' are actually a painting on a canvas backdrop.
For a couple of shots when Echo and Tweedledee are at Mr. Arlington's house, (Harry Earles) accidentally left his wedding ring on his finger.
When Hector and Rosie are bringing home the Christmas tree, Hector is wearing his glasses as they enter the store. Once inside, they are gone. Later, as he brings the tree into the living area, they have reappeared.