At the wedding of some friends of ours
The bride and groom handed out bottles of sparkling wine to various people who had stayed until midnight, and many of these were opened and consumed before we left the premises. One friend decided she was going to steal the easel that was being used to hold up the table plan. It seemed hilarious at the time.

When we got back to the nearby Travelodge, a few friends had managed to gain access to our room, and surprised us as we walked in. The revelry continued. One of the group was the girl who stole the easel, so the easel was still there in the morning, after she had made her way back to her room in the early hours.

We met her in reception, and she was a shadow of her former self. There was more red in her eyes than white, and she wasn't speaking in words of more than one syllable. We handed her the easel, and she looked at it for a moment, confused. Then realisation struck, and wordlessly, she nodded in acknowledgement, and slowly trudged in the direction of the venue to return it.
(sabre-tooth monkey, Fri 27 Apr 2012, 9:29, 1 reply)

I like this
At our wedding, we had free booze. It was my father-in-law's idea and he was generously paying for it. Some of our friends left at the end of the night clasping unopened bottles of Prosecco-ey stuff. They very ashamedly tried returning them the next day, only to be told to keep them and told off by my father-in-law for not drinking them on the night.
( sanityclause is waiting until, Fri 27 Apr 2012, 16:49, closed)