The SF kid making a beeline for the door was the most hilarious part of that scenario.
But I disagree that the American and Japanese kids developed more slowly. All the kids seemed developmentally on target and quite bright; they just got there through different means. The Japanese baby having a meltdown was not only the funniest part of the whole movie for me, it was fascinating to watch. That kid was WAY smart. Her brain knew what to do; she was just too young to have the fine motor skills to do what she wanted, and she lost her temper. And what a temper she had.