My wife 'invented" the best emergency toilet 6 or so years ago. She was in Atlanta with the kids, dropping off a friend at the airport. She had to pee in the worst way! She pulled off at a McDonalds that didn't seem to be the safest place to be. So she took one of the kid's diapers, and "used" it as a toilet while remaining in the minivan. She laughed all the way home about how well it worked, and keeps one under the seat to this day.