One important element is over - the - top situations. For instance, if a mouse is chasing a cat instead of the other way around. This turns the normal expectations upside down. Exaggerated actions of the characters also contribute. Such as a little bird that flaps its wings so hard that it blows all the leaves off the trees. And of course, the use of vivid and comical descriptions, like a frog with a hat that's ten times too big for its head.
First, the use of animal characters in unexpected roles. For example, a turtle that is a superhero. Second, misunderstandings between characters can be very funny. Like when a duck thinks the farmer is calling it for a race instead of dinner. And third, a touch of magic or the impossible can add humor. Imagine a pig that can fly and has to rescue its friends from a high tree. All these elements combined can create a really funny children's story.