99 per cent of them dont create more than 20 per cent of their work what they do most of the time is that they shape it to become a complete animation,the king of it is genta he can take a whole year to take a part from this person,another part from another,himself his work then mix everything together to transform it into a catchy animation
you'll notice that many animation from him become different 6months after when he's found out how to associate the original idea with various other ones into one