A Neverending Reckless Fight

The mouse hit the rat in the head.
This caused the rat to hit the cat in the head.
Which then caused the cat to hit the dog in the head.
But none of this wouldn't have happened
If only the mouse didn't hit the rat in the head
But what drove the mouse to hit the rat in the head?

Before the mouse hit the rat in the head
And the rat hit the cat
And the cat hit the dog
The cow hit the mouse in the head
But way before the cow hit the mouse
The horse hit the cow
And the dog hit the horse
All before the mouse hit the rat

So, the dog started it all
But the dog only hit the horse because the cat hit the dog
I guess all of this hitting started way back
Never ending war

In the corner a tiny flea laughed
He laughed because he bit the animals
So, they all began fighting each other thinking the other did it
All of this from one tiny bite
And one tiny naughty flea

A never ending reckless fight