When the almost exclusively female name on your ID card and mother's misgenderings aren't enough to make people use female pronouns.
Also I met up with some friends to whom I'm stealth, and we were hanging out with a bunch of guys (and one girl) they know. I was on a roll with my comedic streak, and one of the kids goes, "This dude right here is the guy," followed by my friend saying "No, he wants to be the guy" (in reference to the game I Wanna Be the Guy, not having to do with being trans). So I went "Yeah, I wanna be the guy" and he says "But you already are the guy!" and the others overhear and think I said I want to be a guy and go "Wait, you're not a guy?!?! No, bull****, you're a guy. Stop screwing with us man!". I explained the game reference to them and they were relieved, because apparently the concept of me being a girl was utterly mind-boggling and terrifying to them