According to Wikipedia, "Once upon a time" is a
stock phrase that has been used in some form since at least 1360 in
storytelling in the English language, and seems to have become a widely
accepted convention for opening oral narratives by around 1600. These stories
often then end with "and they all lived happily ever after," or,
originally, "happily until their deaths."
As well as being the title of an American fantasy-drama
television series, it was also a French animated series of history lessons
produced for children in the late 70’s. What follows is an episode translated into
English.