Holy FUCK!!
Oh my god that was funny!!! The graphics were well done and the "calm" nature of the lines and fills (being more curvy than spiky) somehow made the ending less predictable. Very good work.
The sound was good, and the screaming was amazing, but the kid saying "I'm learning to read big people books" was incoherent. I had to watch it three times to understand that line, and even then a friend had to point it out for me. It sounded like "I'm learning to read b?? people books" and I couldn't tell what the hell was going on.
The concept was brilliance. It gave me a big giant "WTF" to ponder for several seconds. The only problem was that the adult stood there for about a full second before biting the kid, which took away the mystique a little bit. The quicker the ending was the more "WTF" value you get. However, if you tested it with different pauses I can see how you might have chosen the length of pause you did.