What a fabulous thread! I thought of one to share (though it is relatively tame by comparison).
When visiting NYC with DH (long before the arrival of DD and DS), DH's cousin invited us to dinner at his flat in NJ, overlooking Manhattan, the night before we were due to fly home. He and his wife had a young baby who we met briefly before his bedtime. As soon as their son was in bed, the cousin and his wife started drinking heavily. While dinner was cooking, in the middle of a fairly banal conversation, the wife reached over and gouged a two inch long strip of flesh out of the top of my foot (I was in ballet flats - and I still have a scar) with her fingernail and laughed maniacally. By the time I had mopped up the bleeding in the bathroom, dinner was on the table, so I thought we should stay to eat, even though I was a little peeved at the random assault.
After dinner, DH's cousin's wife passed out on the sofa. DH's cousin brought out the whisky (offered to DH but not to me) and DH declined, saying that we should get a cab soon, as we had to leave our hotel for our flight at 6am the next morning. DH's cousin agreed, then asked us to wait for a moment while he went to the loo, but then he, too, passed out in his bedroom. DH and I began tearing the kitchen / living area apart looking for a phone book to call a cab to get us back to Manhattan while periodically attempting to rouse one of our hosts and worrying that if we couldn't wake them, was it OK to leave them in charge of their (admittedly sleeping) baby.
We couldn't find a phonebook, but after a couple of hours (during which we started seriously discussing whether or not we should phone the airline and change our flights, since things were not looking good), DH managed to rouse his cousin. The cousin insisted on walking us to the ferry terminal, although we pointed out that the last ferry had gone hours earlier, then walked us back to his flat and started to go back to bed. DH physically prevented him from going back to his bedroom and finally got him to call us a cab - which got us back to our hotel with three hours to spare before we had to leave to get home.
It remains one of the most surreal nights of my life.