Laughter-induced faecal-leakage, or your money back

I went to the back of the station and walked up to the person I thought looked most like a drug dealer.
"I want to buy some drugs," I said.
He eyed me suspiciously and said: "You DS?"
"What's DS?" I asked.
"Drugs Squad."
He looked at me in a hard way that suggested that if I gave the wrong answer, he'd break my legs.
I thought about it. I still didn't know what he meant. Drugs Squad sounded to me like a special group of very experienced drug users- maybe I could get a discount.
I said yes.
He broke my legs.
On the plus side, he did give me some Nurofen for the pain.