You know what's funny? When Achilles and I were little, both of our families had "No singing at the dinner table" rules. It's also Maira Kalman's father's first rule.
Do kids have some sort of innate impulse to sing at the dinner table, or is it just the catchiness factor of songs like "On Top of Spaghetti"?
I like to think that kids are so happy to be together with their family that they can't help but sing. But maybe it's just a really good way to irritate parents after a long day's work.