Handy site to bookmark if you're watching a movie and can't hold it - you can look up a movie and it will tell you when it's safe to go to the bathroom. For example, Star Trek has 4 pee times (50 minutes, an hour, 1 hour 20, and 1 hour 40) so you've got lots of opportunities to take a quick break. They scramble the part that you'll be missing so you can come back later and find out the little bits you missed.