Together with her younger sister, Crystal McKellar, she began acting at a young age 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) was followed by her breakthrough in "The Wonder Years" (1988). She has had good grades in math and French. In her spare time she likes to go skiing, swimming and surfing.

Sister of Crystal McKellar, whom she considers her best friend.Graduated summa cum laude from UCLA with a BS in mathematics in June 1998.Had a 1998 paper published in Britain's "Journal of Physics A: Mathematics & General" with UCLA professor Lincoln Chayes and student Brandy Winn that provided a mathematical proof for a theorem dealing with magnetism in two dimensions. Her Erdos number is, at most, four; her Bacon number, by comparison, is two.Is fluent in French.Was a member of the Alpha Chi chapter of Alpha Delta Pi sorority at UCLA.Attended Jason Marsden's nuptials, October 2004.She is of Scottish and Portuguese descent.Celebrity Judge for UCLA Spring Sing 2005.Played the role of "Catherine" in a San Diego production of David Auburn's play "Proof". Catherine is an unlikely mathematical genius who writes a groundbreaking proof at a very young age; McKellar is also an unlikely mathematical genius (she was the only undergraduate invited to speak at Rutgers University's biannual Statistical Mechanics) who wrote a proof at a very young age.Daughter of Mahaila McKellar and Christopher McKellar.Stepsister of Christopher McKellar Jr. and Connor McKellar."ABC Evening News" (1953) named her "Person of the Week" for her book, "Math Doesn't Suck".Did all her own dancing and lifts in "21 and a Wakeup" with partner Jamie Bayard, of "So You Think You Can Dance" fame.Is now a two-time New York Times bestselling author with books "Kiss My Math" (2008) and "Math Doesn't Suck" (2007).One of the few people to have both an Erdös number (the number of scientific-paper authors it takes to connect herself to the Hungarian mathematician Paul Erdös) AND a Bacon number (the the degree of separation between her and American actor Kevin Bacon). Many scientists and mathematicians have an Erdös number, and a great many actors have a Bacon number, but relatively few people have both.