Before he breaks the glass on his door, there is a flashback to his keys in his car. It shows a Schlage style key, yet when Robin Williams picks up the spare key it is a Kwik-Set style key...two very different keys.
In the final scene in the front yard, as Nelson carries the baby, the neighbor's yard shows a blooming dogwood tree and flowering white shrub revealing the Christmas cold-weather scene was filmed in the spring.