I always went to rated R movies when I was under 18. I think around when I was 15 I started to often not be question in many movies theaters about my age. Maybe it was because a few of the theaters I went to were surprisingly lax, one of them only for a few years before they really tightened it up.
Even before I was 15 I was sneaking into movies to see them for free using the back door method, as well as just movie hopping after the movies get out (soo easy to do if they don't check tickets at the individual screen entrances, either just walk straight to another movie through the crowd of people, or walk to the bathroom only to leave and walk into another movie). I'd often by tickets for other movies, knowing full well I wasn't going to see the movie on the ticket I bought if I didn't want to bother trying to see if they are checking IDs/will check mine. When one of the theaters put in machine ticket vendors, you didn't even have to worry about being 18 unless you clearly looked to young when the ticket ripper took your ticket, you'd just buy the ticket you wanted and walk in. Just as often I wouldn't be carded until I guess the movie theater that I mainly went to got more strict (right when I was 18), so I was usually able to buy the ticket I wanted.
I did realize it was based on the comic book, but still doesn't stop me from disliking the film.