Danica and her sister Crystal
, younger by one year, are both actresses and dancers. They both began their careers at a very young age as child stars.
McKellar, together with her sister, began acting in her mother's dance studio. In 1982, the family moved to Los Angeles and a few years later, she appeared in her first commercial. A few guest appearances in The Twilight Zone
(1985) were followed by her breakthrough role in The Wonder Years
In school, she had good grades in math and French. She graduated summa cum laude from UCLA with a BA in Mathematics. While attending UCLA, she was a member of the Alpha Chi chapter of Alpha Delta Pi sorority.
She had a 1998 paper published in Britain's "Journal of Physics A: Mathematics & General" with UCLA professor Lincoln Chayes and student Brandy Winn. The paper provided a mathematical proof for a theorem dealing with magnetism in two dimensions. Her Erdos number is at most 4. Her Bacon number, by comparison, is 2.
In her spare time, she likes to go skiing, swimming and surfing.