Subtract the pointing and add some seriously flexible stomach contortions.
She taught herself the tummy roll after watching Sesame Street where apparently some guest did it, the rest is a bit of a mystery. She always asks "Why are you laughing Daddy?" Which of course makes me laugh more. How the hell can I answer that question?
I've made an effort to always be as complete and honest with her as I can when she asks me questions. She has a basic understanding of sex for instance. Not the act, but only because it hasn't come up yet. It might never, we do live on a farm after all. But she does know that she grew in Mummy's tummy and that she started out as an egg from Mummy combined with a seed from Daddy. She also knows when our rooster is doing that to a hen he's trying to give his seed to her. I guess we will have to have a sex talk at some point, just to make sure that she understands that human sex isn't usually that quick, violent or one sided. :)
When she asks what things are called I also strive to use the real word even if it's polysyllabic. You'd be surprised at how fast she picks up even the most complex words. A four year old's brain has huge portions of it dedicated to language acquisition, might as well take advantage of that while it lasts.
But I am at a loss to explain to her why I find that particular performance so hilarious. I mean it just IS. Sometimes the only honest answer is "I don't know." Of course, it's tricky getting that out when you're snorting soy milk out your nose.