The sky is like a bouncy castle because it's always changing its shape, just like when you're on a pogo stick, but instead of bouncing you get to watch the clouds go by. You might even get a little dizzy from looking up at the sky, but that's just a bonus!
Other times the sky is also like a bouncy castle: when the sun sets, it's like someone lit the whole place with a giant firework, but then the moon comes out and it's like, "Hey, calm down up there, we can still have some moonlight!"
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