Deliberate "mistake": During the final montage, we see Erik and Joyce in bed together, and the next sequence is of Teddy talking to his baby brother. This was to show that they got back together and had another kid. The mistake is that Teddy would've been a year older by that time, and so would've looked a little bigger, although there is also the fact that the actor who played Teddy (Dakota Goyo) was between 7 and 8 for the filming.
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