I've had a problem that has plagued me since I was a teenager: Apparently, I look a lot younger than I actually am. I was still getting carded for R-rated movies well into my 20s. After we moved into our house, I'd open the door to door-to-door salespeople only to have most of them ask me, "Are your mom and dad at home?"
It hasn't happened in quite a while, so I thought, "Well, maybe having a baby and getting cancer have finally aged me." Today, a guy from the water department came by to hook up some new water-meter thingie. He explained what he was going to do, and then said, "Um. Are you over 18?"
This was kind of an annoying problem when I was 17 and just wanted to see The Hand that Rocks the Cradle without being harassed. Now it's just fun.