I once had a session that became infamous amongst my group at the time. There was a magic forest that only the elves knew the way through, but no elves had come through for a while. One of the players was an elf, and I had given him a note explaining that there was a path featuring a sequence of specific species of trees, oak then spruce then elder, that sort of thing. He was supposed to go in the direction moss grew on said trees until seeing the new species, then look for the moss again, and so on and so forth. I expressly noted on the note that if he didn’t see the exact sequence of trees I gave in the note, “something had gone seriously wrong”.
Of course, the idea was that something had gone wrong and the path through the magical maze forest was screwed up, hence no elves arriving recently. My reason for setting it up this way was so that the elf would lead the party into the woods, he’d try to find the path, realize the path was broken, tell the party, and then they’d get down to the business of figuring out what was wrong and fixing it. You know… start the adventure.
Instead, what ensued was an entire multi hour long session of nothing happening. The elf would lead them. I’d tell him the trees they were seeing, out of order. He’d just keep following the moss, the “path” as he always did. I started emphasizing the wrongness of the trees he was seeing. He kept leading the party. I nudged him harder and harder. He just fucking kept going. The party was confused of course, as the whole path thing was supposed to be an elven secret that they didn’t share. And the elf player just kept ramming the entire party’s heads against the stupid wall for real world hours and I couldn’t stop it until I eventually dropped the 4th wall and flat out said this isn’t working, I’ve told you it isn’t working, please do something else! And then we had to end the session and start again next time.
It was incredibly frustrating in the moment, but it actually worked out well for the game as a whole. Became a running gag, a source of a lot of laughs, and it somehow ended up hammering in the point that something was wrong with the world and forest far more effectively than it might have if it had ended quicker. So good times in the end after all…