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Apple Mary, created by Martha Orr, is a comic strip that, if you believe official King Features Syndicate sources, only ran from 1932 to 1939 and has no connection to any other strip that they own and distribute. They did not acquire it from Field Enterprises Syndicate who acquired it from Publishers Syndicate, they did not transform it into Mary Worth, and the two strips are entirely separate entities. Of course, anyone who knows anything about the actual history of the strips knows this is absolute hogwash. In 1939, after Martha Orr left the strip, it was briefly titled "Apple Mary: Mary Worth's Family" before being changed to "Mary Worth," and Allen Saunders, the cartoonist who took over for Orr, has stated multiple times that he was given the strip Apple Mary and he transformed it into Mary Worth. And, of course, the full name of the main character in Apple Mary is named Mary Worth. The modern Mary Worth is certainly a very different strip than Apple Mary was, but it's undeniable what it started as. Why King Features denies this is anyone's guess, but I imagine it has something to do with not wanting to credit or compensate Martha Orr or her estate.
As an example of how different the strips are, I don't think any modern Mary Worth strip would show a small child getting a present from Santa Claus, kicking him because she didn't like it, and using the toy to hit him in the face. Or maybe it would. If so, maybe I should start reading more Mary Worth.