Heroin is fun

Heroin is fun*. It really is.
By which I mean, revulsion and fear regarding heroin use are so strong in so many people that even mentioning heroin tends to provoke a strong response. Also, not everyone shares my sense of humour.
Case in point: at work I'm getting one of my many drinks of high-caffeine cola I require to make it through a day. A drone cow-orker feels compelled to comment that this is an unhealthy thing to drink. I get really fucking sick of this type of comment. Usually I'd pretty much ignore it but I decided to respond.
"Well, given that I actually have very few bad habits I think I'll survive. I don't smoke and I rarely drink alcohol so let me have this vice."
She seems prepared to stop with the unwanted platitudes at this point so I probably should have left well enough alone. But she really annoyed me. So I followed up with:
"In fact, if it wasn't for the heroin I'd be leading quite a clean lifestyle."
This little throwaway line leads what I will charitably call an uncomfortable silence. She's staring at me with a look that seems to be equal parts shock, horror, revulsion and pity. I could do without the pity.
The first thought that goes through my head is "She can't possibly think that was anything but a joke. She doesn't have to think it's a funny joke but she must know it's a joke." Then I think about it for a while and realise this is the sort of unimaginative lump who gets all their "information" from nightly current affairs tabloid shows. She is clearly waiting for me to grow horns.
In situations like this, my mind tends to go a hundred miles an hour. I mentally run through multiple scenarios of how this could play out in seconds. None of the scenarios I was imagining were ending well. Every variation of "It was a joke!" had me looking like a junkie in denial. Or maybe a junkie who was getting agitated because he was strung out and in need of a hit.
Then the evil part of my brain took over. The part that thinks it's funny to fuck with repressed people. Hey, whispered my evil brain, if she's gonna treat that obvious joke seriously then go the whole way. Freak her the fuck out. Say something about "watch out for used syringes near my desk". Ask her if she can loan you some money. Or just roll your eyes and then collapse.
That last one started to sound real good. It would have a double bonus of scaring the cow-orker and I wouldn't have to finish the conversation. I could just lie on the floor until she ran away. Approximately three nanonseconds before I put this plan into action she backed out of the kitchen. I didn't hear running but it's distinctly plausible that she was sprinting for safety as soon as she was out of sight.
In retrospect, if you've just told someone you're using heroin, staring at them glassy-eyed until they leave the room isn't the best way to convince them you were joking.
*NOTE: This is not an endorsement of using heroin. If you're stupid enough to think it is then you're too fucking stupid to accept this disclaimer. Let's just go with "I'm a horrible and irresponsible person". And fuck you.