It took a lot of discussion among friends/helpers to decide on a punchline, and even now I'm still not sure of its effectiveness.
I've had the opportunities in my studies to interview several children. They were all so bright and well-behaved and sweet like you'd never believe! In case you don't know, if you were to stroke a baby's palm with your finger, the tiny hand will grasp it tight (an evolutionary reflex). Seeing the tiny fingers hold yours firmly is so adorable it makes your heart melt.
Maybe it's because of the setting, because I can recall many occasions where I see demonic children tormenting their parents in other public places. That was partly the inspiration for this strip.
Btw, here are the other punchlines I considered.[link][link]