Alice has been grappling with the concept of getting bigger and bigger lately. Sometimes she'll give us random factoids like, "When I get bigger, I'm going to wear a bigger coat!" Most often though, it comes up when we're explaining why she can't do something yet. She's more accepting of limitations like not being able to sit in the driver's seat of the car or read books without pictures if she knows she'll be able to do it when she gets bigger.
However, it has become clear on some occasions that she thinks that as she gets bigger and bigger, we'll get smaller and smaller. This comes up mainly when discussion chairs. She likes to tell Zac that when she gets bigger, she'll sit in his chair, and when he gets smaller, he'll sit in her chair (a booster seat).
We were trying to explain to her today that people don't get smaller, they just get bigger and bigger until one day they stop growing and stay the same size. I added the caveat that although people might not get taller, they can still get fatter. She grasped this concept immediately, and said, "Like Mommy's belly!"