From Muppet Wiki

Tattypoo is the white-haired Good Witch of the North in The Muppets' Wizard of Oz. As played by Miss Piggy, she is very fond of the Munchkins and likes to drop in for a cuddle or two. She also seems to be fond of penguins.

Tattypoo and her sisters (the Wicked Witch of the East, the Wicked Witch of the West, and Glinda, the Good Witch of the South) once formed a popular singing group called the Four Little Pigs.

In L. Frank Baum's original novel, The Wonderful Wizard of Oz, the Good Witch of the North was not named Tattypoo; in fact, she was not named at all until the twenty-second "Oz" novel, The Giant Horse of Oz by Ruth Plumly Thompson. In the popular MGM movie based on the novel, the Good Witch of the North was eliminated entirely, and her role was merged with that of Glinda.