I'm just going to call this one Dumb As a Stump.
A girl is told to stay away from Mother Trudy.
But the girl goes to visit Frau Trude anyway to find out what all the fuss is about. When she reaches Mother Trudy's door she is ashen as she meets the old woman. When asked to explain what is troubling her the girl says she has seen a black man on her stairs. Mother Trudy insists it was just an old coal burner. A green man is waved off as a huntsman, a blood red man is merely a butcher and then, just before the girl knocked on Mother Trudy's door, she saw the Devil through the window prancing around.
The jig is up. Mother Trudy turns the girl into a block of wood and tosses her into the fire.
"That really does give off a bright light," Frau Trude remarks. Dim in life, bright in death, dumb as a stump.
I will say this, as cautionary tales go it's at least short and to the point. If you are told to stay away from the old witch, then stay away. I am a little curious as to why, if the people knew that Mother Trudy was as bad as all that why they just didn't tell our dim little star that the Devil lived in the house. Would she have been equally curious? After all, having seen the Devil through the window she continued on to knock on the door.
Unless her family wanted her to go visit Mother Trudy, knowing that her curiosity would get the better of her. Seems a bit harsh as population control