See, I think that post misses the whole point of this thread. This isn't "any tickling idea whatever," this is SUPPOSED to be for Impractical ideas, for interesting and unique tickle scenarios.
And there's nothing wrong with imagining someone trapped halfway-in and halfway-out of a wall, or trapped in a window, or locked in some sort of coffin or magician's box. In fact, I rather think it would be cool if you had two people trapped like that, 69, so that neither could see the other. Could be M/M, M/F, or F/F or perhaps it is dark and they can't see the color and sex of the other person. You can have one tickling the other, or both having a ticklefight, or one is tied up and forced to stare at someone's feet while he or she has their own feet tickled. Perhaps they rotate torturing each other. Maybe a scientist has tied up a bunch of people in a daisy-chain, and you can tickle the feet sticking out of the left wall while your own feet are inside the right wall, being tickled by someone else.
If someone here enjoys contemplating one of these ideas, or has never heard it before and has now been given a new variation, then I'm happy, and I don't care how silly or impractical the idea is. If even one person that was bored is now entertained, then that's a good thing! 🙂