Plot hole: Throughout the film we see several characters talk about how there's no Christmas spirit and how nobody believes in Santa anymore. If, in this universe at least, Santa does exist, it's almost impossible for people to think this. If the parents deliver the presents then how do they explain the excess gifts that Santa brings? We know that Michael is on the nice list because Santa shows him towards the end, so Michael must get presents from Santa. There is no way that Walter can't believe in Santa then because Michael gets gifts from him every year.
Suggested correction: Emily and Walter probably just thought each present Michael got from Santa was from the other parent. I'm not sure if Walter got him presents or not but you can see that Emily did as she's seen walking home with presents when she's on the phone with Walter.
That is highly unlikely. When my daughter was "believing in Santa" age, my wife and I always talked about what we were getting her, so we didn't duplicate. Plus that theory wouldn't work for single parents.
It is very likely because it's obvious Walter is not in the Christmas spirit like his wife and Michael are. Plus it's obvious Walter is not focused on his family at the beginning of the movie so it's safe to assume the original submission is correct.
