The stupid helmet is a headgear, preferably a Packers - helmet, one is made to wear when a jury of friends find one of their peers guilty of comitting an act of stupidity. It originates from That 70's Show and is indeed the greatest mark of shame there is.
Defendant, you were caught toilet papering my sister's car. As this car also belongs to me, I find you guilty of committing stupidity. According to the traditions of our reverred law, you must be punished to its full extent. This means the Stupid Helmet.