Good question, which has just clarified in my mind one important aspect of the definition of a joke- it is intentional! Sure dimwits (or should we say, "lucky" people) can find humour in antything, but that doesn't make it a joke.
And jokes can be pretty serious too, as statements for example. But again, to qualify, with intention and there has to be humour of course, even if only a slight touch of sarcasm.
So it can be immediately and compellingly obvious that you are joking.
I like the slightly more obscure, teasing humour myself, where you aim to play a brief trick on the mind (not your own lol), catch it out, make it temporarily think/assume one thing, and go through a rapid process of ping-pong realisations to "get" the joke.
The longer this takes, the more stops along the way, the less control the (victim haha) has over everything until everything clicks and it all comes back. The better and warmer the humour, the more completely positive can be the mental and emotional effect, a great therapy.
So to me that was always what humour was about- that magic where reality is escaped for a moment. Just a brilliant second away is like a holiday at times, such is the power of humour.
Now, I only have one more thing to say.....
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