Three nuns passed every day through a street that led them from Church  to a Reformatory. They noticed a parrot that stood at the entrance of  a big residential house. Every time they passed in front of that house,  the bird would pronounce three sequential colors.

One day, they heard "yellow, blue, black." One of the nuns noticed  that those colors perfectly matched the colors of their underwear.  She mentioned her discovery to the other two nuns, but both were  reluctant to believe that could be possible.

The next day, they all wore black underwear and passed in front of  the house, and very precisely the parrot spoke, "black, black, black." Hearing that, the three nuns were astonished!!. One of the nuns spoke  up: "Girls, tomorrow we are going to trick that bird." Saying that,  she recommended that the next day, none of them should be wearing  any underwear under their vestments. Respecting their agreement, the  next day they wore no underwear, and proceeded to pass in front of  the parrot's house.

They peeked at the bird. At the beginning, the parrot looked a bit  puzzled, he swung back and forth on the cane he was perched on. Then, after a while, the Parrot spoke: "Straight, Straight, Curly!"