 The Aliens are based on actual ancient cave paintings in Tassilli,  Sahara. These drawings were referred to as "the Great Martian God"  by archaeologist Henry Lohte. Author Erich Von Daniken mentions  these ancient visitors in his book "Chariots of the Gods" and  Swedish comic book writer, Rolf Gohs wrote a spooky story where two  boys have a close encounter with this "Great Martian God" in his  classic comic book "the Mysterious Two".