Three Milky Musketeers
"Hang on — that's a Milky Way!"
"No it's not, Milky Ways have caramel."
"They do not! Mars Bars have caramel. Milky Way is just fluffy nougat. Eat it between meals without spoiling your appetite, and all that stuff."
Well, it turns out we're both right. Wikipedia spells it out:
UK Milky Way = US Three Musketeers
UK Mars Bar = US Milky Way
And stranger yet, there was a US Mars Bar, now called the Snickers Almond Bar (US) or Mars Almond Bar (UK).
In other chocolate news: the renaming, 15 years ago, of the UK's Marathon bar ("packed with peanuts, Marathon really satisfies") to the Snickers brand prevalent in the US and elsewhere still rankles. So, odd then to see the Marathon name resurface, attached to the really rather crappy Snickers Marathon energy bar.
All that said though, the US does have the best junk-food chocolate ever: the Reese's Peanut Butter Cup.