A guy goes to the pharmacist and says, "Listen, these two girls are coming over this weekend, and they are hot, very hot. Would you have something to get me going all night? It's going to be a hell of a party."
The pharmacist goes in the back room, comes back with an old dusty bottle and says, "This stuff is potent: drink only one ounce of it, and I guarantee that you will be doing the wild thing all night. Let me know how it goes."
The weekend goes by and on Monday morning, the pharmacist goes to work and finds the same guy waiting for him on the door-step. The pharmacist says, "What are you doing here so early? How was your weekend?" The guy replies, "Quick, I need Blue Ice (muscle pain relief).
The pharmacist, knowing what the guy had been doing all weekend, says, "Are you crazy, you can't put that on your penis. The skin is way too sensitive."
The guy says, "No, no, It's not for that, it's for my arm."
Pharmacist: "What?? What happened?"
Guy replies, "Well...I drank the whole bottle of your potion."