I once worked somewhere where mysteriously a toilet would always be blocked before 9am by someone. We're talking about feces covered with a ridiculous amount of paper towels, made soggy from flushing attempts, sometimes with overspill on the floor, thus making the toilet unusable to others. It was busy office floor with say 120 people on that floor. I figured it was the same person and suspected someone. I don't recommend doing this if you're unhappy in your job. It's not fair on others to deal with that every day.