Being mistaken for a child

Many petite women are mistaken for being younger than they are, but have you ever been mistaken for someone much, much younger? Over at the Petite Power Livejournal group, a poster wrote about getting a kids' menu at a restaurant. Or, maybe a server or bouncer asks to see your ID at a club, and then tells you that he/she thinks it isn't real. Or, they just tell you (usually not so politely) that you're too young, without even asking for your ID (which I think is wrong. They can't just assume. If they don't know, they should ask for identification). How would you react? Has this ever happened to you?