Deliberate mistake: When Jonathan and Emma are beginning to know each other, they make their way to the wood shop, where Emma picks up an "air powered tool". The tool is a staple gun, but shoots two 3" nails close to Jonathan.
Deliberate mistake: In the scene where Emma and Jonathan are playing "Dress up", Jonathan is seen playing the organ. Then the shot pans to Emma dancing on the balcony. If you pay close attention at this point, you can see a heavy contrast in color.