My belly button popped early with this pregnancy. When I was pregnant with CR, and my belly button popped out, I was horrified to discover that on the inside of my belly, lives a scary looking little mole. CR is observant, and soon after the mole reared its ugly head, he made up his own reason why the darkened bump looks the way it does...
When I ask him about the baby in Mommy's tummy, he points to the mole, and says that it's the baby's foot, kicking out from the inside...that is the only thing that is cute about this lovely side effect of pregnancy...
(image from here)