Long ago, in the early 1980’s, our AD&D group was wandering through a dungeon and came upon some loot. Included was a vial with some indeterminate liquid in a very fancy container. We all passed it around, sniffed it, putting a drop on our finger, drop on the tongue, but we couldn’t reach a conclusion as to what was in it. Of course no one had any Identify spells - those were saved for the end of the adventure!
After a minute or so, our ever-impatient Chaotic player says “Fine! I drink the whole thing!”.
The DM blinks and says, “what?”
The player says “I drink it! Now what happens to me?”
The DM smiles, and starts laughing until he can barely breathe. When he calms down enough, he finally manages to say, “that was an Oil of Slipperiness!”
Which, of course, worked. Very well. A lesson in what happens when biology meets magic.
The player immediately had the entire contents of his digestive system, top to bottom, dump onto the floor. We all got a roll to see how fast we could jump back (we all made it out of the blast zone in time). The poor player’s armor was stained completely brown from the waist down.
For the next three days (until the DM finally took pity on him), everything that went in his mouth immediately came out the other end. He gave up wearing armor, leaving it all behind. We all had to make sure we were always upwind or far enough ahead of the smell.
I would like to say he learned from the experience, but I bet that the rest of us learned a lot more than he did!