Once, I got out of the shower just as The Squeeze's mom's Man-Friend-at-the-Time opened the bathroom door. It was... bad. That'll teach me not to lock the door.
(True: Port-a-Potties are gross. That's a given, but also their "locks" are broken half the time, and you have no way of knowing. Have a friend guard the door if you don't want a stanger to see your business. Or better yet, hold it for actual plumbing.
Tangent: Who the hell thinks that a sheet of metal is an acceptable substitute for a mirror in an oversized diaper pail with no light? Honestly!)