At the age of six, Mary-Kate and Ashley Olsen began starring together in TV, film, and video projects, which continued to their teenage years.Through their company Dualstar, the Olsens joined the ranks of the wealthiest women in the entertainment industry at a young age.In early 2004, Mary-Kate and Ashley had a cameo voice role in an episode of The Simpsons as the readers of Marge's book-on-tape, The Harpooned Heart.Also in 2004, the twins starred in a second feature film, New York Minute.Upon taking control of the company, Mary-Kate and Ashley made moves to secure the future of the company by releasing products that appealed to the teen market, including home decoration and fragrances.The Olsens have appeared on the Forbes "Celebrity 100" list since 2002; in 2007, Forbes ranked them (collectively) as the eleventh-richest women in entertainment, with an estimated net worth of US 0 million.In 1992, Mary-Kate and Ashley shared the role of Michelle Tanner when they guest-starred on the Full House crossover episode of Hangin' with Mr. While starring on Full House, the Olsens also began appearing (as separate characters) in films for video and television.The first such film, To Grandmother's House We Go, debuted in 1992 and featured cameos from several other Full House actors.
The Olsens had a clothing line for girls ages 4–14 in Wal-Mart stores across North America, as well as a beauty line called "Mary-Kate and Ashley: Real fashion for real girls".
1998 also saw the release of Billboard Dad, the first of a new string of direct-to-video films starring the Olsens.
The final such film, The Challenge, debuted in 2003.
Mary-Kate and Ashley were popular figures in the preteen market during the late 1990s and early 2000s.
Their names and likenesses extended, not only to movies and videos, but to clothes, shoes, purses, hats, books, CDs and cassette tapes, fragrances and makeup, magazines, video and board games, dolls, posters, calendars, and even telephones and CD players—with a market share made up mostly of the tween demographic.