Hello all! First time poster in this thread. I have read the other thread, as well as this one and I think it's about time for me to contribute.

I am the DM for a Pathfinder group who seem to delight in screwing up as massively as possible. Case in point:

Cast: who and what the players were is of no consequence as they all did the same thing (keep in mind, however, I did have 3 10 year veterans of DnD who really should have known better. )

We had just begun the Tomb of Horrors and, though many shenanigans ensued, this one takes the cake. I shall spoiler the rest in case you haven't run the Tomb of Horrors.

Spoiler
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Somewhere within the Tomb, affixed to a wall, there is the relief of a demon's head, jaws agape, with naught but darkness filling its mouth. The relief is or is not green, I can't recall, but my players sure believed it was and, thanks to a cryptic poem, they believed it was their ticket out.

So they inspect it, check it for traps, detect magic on it, even throw things into the mouth. After witnessing a few tossed coins being sucked into the mouth, the players decide, as a whole, that the mouth is obviously a portal and they should climb into it.

The first up is the rogue (one of two in the party so no real loss) who climbs up to the mouth, moves his head towards the mouth and is promptly pulled off his feet and sucked in. After calling his name and receiving no response, the other party members huddle up and have a lengthy conversation about what they should do next. I'm confident at this point that someone would see the nonsense of their plan and put a stop to it. At the end of their conversation, one of my Veterans says to me, "I'm crawling into the mouth."

I'm standing there, mouth literally agape, scrambling to find a way to stop him without breaking immersion and completely drawing a blank. So I just watch in mute horror as yet another character is sucked into the mouth.

At this point, everyone is set on crawling into this thing, so I spring into action. I give the relief a palpable aura of evil(party of good who should have thought twice), everyone near it is feeling uneasy (no save), and I'm forcing will saves on anyone who even attempts to touch the head. Sadly, all for naught.

Eight characters, one at a time, willingly crawled into this head and, short of Deus Ex Machina, there was nothing I could do.

After the last character had crawled in, there was a moment of silence. The party waited in eager anticipation of what lay next in the tomb, I sat in stunned horror at what had occurred. I stood up, closed my books, and said, "Congratulations everyone, you have all willingly crawled into a Sphere of Annihilation," then walked out.

At the time, not so funny. In retrospect, we laugh everytime we talk about it. It's become one of those things in our group where no matter how bad you may screw up an adventure, it's never quite as bad as the above story. Hope you've all enjoyed! Cheers.