In the UK, according to the Macmillan online dictionary, it is a word used to indicate that someone is unintelligent, stupid or silly; a fool, buffoon or clown. Its origins are said to be from the cockney rhyming slang expression, Charlie Smirke (= Berk, which in turn is earlier rhyming slang; Berkley Hunt = the unmentionable - think about that next time you call someone a charlie or a berk...). Charlie Smirke was an English jockey, who was a leading rider and racing celebrity from the 1930s-50s.
As so often with Cockney rhyming slang, the logic of the derivation is not always obvious. Whilst current levels of usage are hard to determine, it remains widely recognisable in the UK. The connotations of its origins are clearly unfortunate, however they were not of my doing, so I hope no-one feels it necessary to make a song and dance about them.
There are, of course, alternative uses of the term 'charlie'; cocaine, for example, and as shorthand for the Viet Cong during the Vietnam War. The latter usage is said to be as a consequence of Victor Charlie being used as the military code name for the Viet Cong and subsequently being shortened to Charlie.
That is enough language history, I think, now can we get back to dress code infractions and dining disasters?