Why Is the Earth Round?

Hi, my name is Karoo and I'm five years old. Why does it seem like when you're biking, driving, and walking, this earth seems like it's flat, but it's actually a round circle? And then Ellie, who's seven and lives in Middleton, Wisconsin, wants to know why are all the planets spheres? Why aren't the cubes or pyramids or some other shape? Once again, it's that that that dastardly gravity. So gravity is everything gravity, John, no, not everything's gravity. But, you know, gravity is the big it's the big bully of the force in the universe.