Do you mean as a way of illustrating an "average" person? It's a common thing to 'create' people in order to help children understand more complex ideas from a relatable viewpoint. For instance life in a 13th century English manor-village is more easily understandable if you create a villager who's life the children can follow.

Or do you mean creating someone who had an effect on history as a whole but never really existed, like a fake king or something?

There really was a Johnny Appleseed, but he was nothing like the myth. Compare the actual Davy Crockett to the character in the TV drama. Do the same with Daniel Boone. And yet, these people were taught as fact in schools in the 60's, and likely later. If you think about it, you can find dozens of examples. They all make very nice propaganda, just like the figures you mention.