I'd considered cosplaying once or twice, but I'm not comfortable getting so much attention from strangers like that, haha.
2-3 years ago I was browsing the Artist Alley and just happened to pass by some guy advertising his comic from his table - so he persuaded me and a nearby woman to listen to a summary, handed us some copies to browse through; the protagonist, he said, was a nymphomaniac, and while I don't remember the details of the plot I remember I got the impression this was probably one of the more sexually explicit comics.
And then the woman interrupted him, pointed at me, and said something along the lines of: "I don't think she's old enough to be hearing things like this."
I'm used to people underestimating my age - at this point in time I was often mistaken for an elementary/middle-schooler - but God, that patronizing tone in her voice, I just had to tell her: "Oh, no, I'm sixteen, miss."
And then her jaw dropped. I remember her expression vividly. The guy raised an eyebrow at her like he'd won an argument. It was hilarious.