There's some sort of joke here, but I'm ... just not seeing it. Oh well.

She's as flat as a board.

Well, yeah. I was playing dumb. Touché!

Would it be wrong to put forward the idea of an "inside_joke" tag for something like this?

I think the joke is meant to be obvious.
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...DOH! You got me, you prankster.

Awwww, poor girl, she's crying.

In my opinion too, a "joke_inside"-like tag could be great for this kind of pics