my dad dropped me and a bunch of cousins off at my first R rated film, Double Impact, when I was 10. And when I say dropped off I mean he barely slowed down long enough for us to open the door and hop out before he pulled off. The dude at the ticket counter got all righteous on us, how he couldn't sell tickets to bunch of 8-11 year olds for an R rated film, blah blah blah. This was in the days before cell phones so I had to wait for my dad to get home to get him to come back and pick us up. He asked to speak to someone who worked there (was the front office guy, i guess the manager or something, whoever let us borrow a phone), and I don't know what he said, but I'll always remember the look on his face and how red it got.
Thinking back on it now, I imagine that my dad took the opportunity, first time the house wasn't filled with brats all weekend, and he was half naked and about to be balls deep in my mom, and said as much to the movie ticket guy. Anyway he immediately let us buy the tickets and watch the movie.