You can pop your own popcorn and sneak it in (maybe a 100 calorie bag?).
My favorite thing to do is bring dinner to the movies and eat it there. My fiance and I sometimes go to subway or blimpie. I'll use a big bag and I can sneak in two subs + two drinks that way
Saves money, you're eating healthier and you're not eating an "extra" snack you might not really need.
I've also made myself a wrap or sandwich and brought it. I'd much rather have a meal than a little snack.