MJ had a bit of difficulty with the concept of opening presents. Sitting on them was about as far as she got. Her birthday was a blast, particularly by the time we go to the opening presents phase. Everyone had eaten, everyone was satiated, I could finally relax and enjoy some MJ time.
On a side note, this is the face that DH and I have started to make when we're provoking each other, doing something we know we're not supposed to do. Someday she'll be embarrassed by this, but we'll continue to explain that she started it.