jackhelmet
A person so thick-headed they think a jackass is a type of sandwich and a jimmyhat is a hat that eats hats.
My friend is a jackhelmet. He tried to build a robot out of Legos and it exploded.
My brother is a jackhelmet. He told the teacher he was a wizard and got sent to the principal’s office.
My neighbor is a jackhelmet. He tried to plant a tree in the middle of the street and got fined.