That I'm a stoner.
No, seriously.
Irl my expression's kinda dull and droopy sometimes, mainly because I don't get much sleep and I get exhausted from social interaction really quickly. I guess it's not that bad most of the time; I just look like I'm halfway between pissed off and bored. But when I'm really tired, particularly the mornings, my expression does look a little akin to that of a stoner, I guess. Since I don't care how I look for the most part, though, I don't do much to hide it. However, it does piss me off when people take that flimsy evidence as enough to make the assumption that I'm a drug addict. I mean, seriously, come on!
I can't count how many times an actual stoner's crossed me in the hallway and was like "Yo, you stoned or something?" or "Yo, wanna smoke some pot?"
I'm not sure why it pisses me off. Maybe it's because I'm so resolute about never trying any drugs; ever.