Crystal took her first dancing classes (tap) when she was three years old. This led to the beginning of her professional career, which started with commercials at age 7. About the time she was 12 years old, Crystal stopped interviewing and auditioning for commercials; explaining that "they're like huge crowded cattle calls...". At age 11, she had her first acting role on television in Fatal Judgement (1988), a movie co-starring Patty Duke. Later, at age 12 and beyond, she went on to make occasional appearances on Les années coup de coeur (1988), a show in which her older sister, Danica McKellar, co-starred. At the age of 14, Crystal McKellar appeared in her second made-for-TV movie, Judgment (1990).