I took LO a couple of times when she was first born because the theater had special movie times specifically for new moms. You could bring in strollers and they kept the lights up a bit so you could see/nurse/etc.

But we hadn't taken her to a movie since that time. I took her to watch Inside Out this weekend on a whim and she did great! She'll be three in November and was very well behaved. I brought a ton of snacks and she ate all of those. We took one quick trip to the potty and had to be convinced to go back in, but she finally agreed and we finished the movie successfully. She stayed in her seat most of the time but spent a little time in my lap or sitting on the step right next to my aisle seat.

When did your LO start watching movies in the theater?