A young Catholic woman had recently been wed to a man whom she loved very much, but she still liked to go out and flirt with men and kick up her heels. When her husband had to go away on a brief trip during Lent, she decided to take advantage of his abscence, despite the religious occasion.
She went to a local dancehall and proceeded to go around the floor with every good-looking man she met. There was one man, a handsome vaquero whom she had never seen before, who attracted her especially, and they danced exclusively with each other for some time. But finally she noticed that something was wrong with his feet, and when she took a closer look, she realized that they were not human, but the clawed feet of a chicken. She cried out, "El diablo!", crossed herself, and fainted dead away. The devil lingered for a moment, smirking at her prone form, and then disappeared in a flash of sulfur.
Note: In some versions the devil doesn't have chicken feet, but the more traditional cloven hooves. But I think chicken feet are scarier, so that's the version I used here.