A smothered wagon is similar to a covered wagon but you shit under the blankets instead of just fart. One could also shart under the blankets to qualify as a smothered wagon.
Kind of like a dick wagon. Instead of a wagon full of dicks, tis a wagon full of pricks. Otherwise known as a Pierre or a Leeham. If you are called a prick wagon, you should just cry for the rest of your life.