During a scene in Puss in Boots (2011), Puss and Kitty jump onto a cloud where Humpty jumped a moment earlier, and some rain falls from the cloud. Why does that happen? Is it to make it more "realistic"? Or is it a joke that I missed?
No, hitting, jumping, or punching a cloud does not make rain fall out. Air planes go thru clouds all the time without rain happening. It's a visual gag, a joke in a cartoon movie for the sake of a joke.