Danica McKellar is an American actress, mathematician, author, and mathematics education advocate. She is best known for playing Winnie Cooper on the television series The Wonder Years and has also appeared in The West Wing, How I Met Your Mother, The Big Bang Theory, and numerous television films. McKellar graduated summa cum laude from UCLA with a degree in mathematics and co-authored mathematical research that led to the Chayes-McKellar-Winn theorem. She is also a New York Times bestselling author of mathematics books for children and young adults and has worked extensively to encourage young people, particularly girls, to develop confidence in mathematics.