Where do ideas come from? That’s easy. Sketchbooks.
I did this sketch of a mama pig and her piglets at the county fair. What a job it must be, I thought, to nurse that many babies all at once.
Some time later I was inventing some aliens for a science fiction paperback cover. I went to my sketchbooks for ideas. The pig suggested the idea of an alien mother who gave birth to a lot kids at once. Fortunately she’s well equipped to feed them.