- Is it just me, or does Mr. Wonka seem a few quarters short of a buck? - I’m sorry, I don’t speak American. "a few quarters short of a buck" suggests something incomplete or lacking. It is one the (jokey) euphemisms for being slow in thinking, or "stupid" which seems to be a taboo word nowadays. So the first person is suggesting Mr Wonka might not be a particularly sharp minded guy, and the other person is essentially saying "I'm sorry. I don't want to talk about it" in a roundabout way which is polite but still sarcastic, probably offended by that suggestion. Since "American" in this sense is not an established word, they probably mean "Don't give that nonsense/bullshit".

a buck=a dollar, it means the same as "A few sandwiches short of a picnic", or "not the sharpest tool of the shed"

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