In the early 20th century, American author Edgar Rice Burroughs was already a legend. While his biggest selling book at the time was about a feral king and his battles through the jungle (Tarzan), Burroughs was also well known for his science fiction series about the adventures of a confederate Virginian transported through death to Mars.
The exploits of John Carter caught the eye of up and coming animator and later known as legendary animator Bob Clampett (Loony Toons and creator of Porky Pig). Clampett approached Burroughs wishing to make John Carter of Mars a full length animated short.
Unfortunately, this was long before the success of the now legendary Superman shorts, and the project never fully got off the ground. However, I found some impressive test footage and artwork provided by his son Jon Burroughs that is amazing. When you watch the clip, be sure to keep an eye out for the innovative use of oil painting and the level of detail in the action scenes; it's a sight to behold.
Also check out this awesome artwork and concept sculptures done by Jon Burroughs for the project!
You can find much more at John Coleman's personal site, but I have to say this blew me away. I really can't wait for the movie now.