In 1976, Spinning Wheel Antiques and Early Crafts Magazine published an article called "Sunbonnet Babies Encore". The article explained how to distinguish various sunbonnet babies by illustrator. There was even a design with the various styles of sunbonnets and who made them. It sounds ludicrous, doesn't it?
Bertha Corbett Melcher is a great example of what happened to a lot of illustrators. Whenever an illustrator became successful, there were always folks who tried to capitalize on the success of the original work.
Some just followed the example and created similar characters like Dorothy Dixon who did a series of illustrated postcards that were popular in the early 20th century: