clipped from: www.chocablog.com   
First off, I do need to explain to our American readers that what you know as a Mars Bar and what the rest of the world knows as a Mars Bar. This (proper!) Mars Bar is similar to - but not exactly the same as - what you know as Milky Way in the U.S. And what the rest of the world knows as a Milky Way is more like your 3 Musketeers bar… which in turn, is quite like our Mars Flyte.

Mars Bar

With that out of the way, we should talk a little about the history of the Mars Bar. According to Wikipedia, the Mars Bar was invented in Britain (Slough, of all places) by an American - Forrest Mars - in 1932. Historical documents show that it is the only interesting thing ever to have happened in Slough.