Trivia

She and her sister became the youngest self-made millionaires in American history before they were 10 years old.

During the filming of La fête à la maison (1987), she acted out the comedic scenes while Ashley took on the more serious ones.

In real life, she and Ashley are very close to John Stamos, who played their uncle Jesse on La fête à la maison (1987).

Close friends with the late Heath Ledger.

At age 6, she and Ashley became the youngest producers in history.

Mary-Kate and Ashley decided to quit acting for good and focus on their fashion careers. (March 2012)

During the earlier seasons of La fête à la maison (1987), the producers did not want this known that Michelle was played by twins, so Mary-Kate and Ashley were credited as Mary Kate Ashley Olsen.

She and Ashley both missed their high school prom to host Saturday Night Live (1975). The cast made this up to them by giving them a fake prom when they did their monologue.

She and Ashley both had to wear fake teeth during the later years of La fête à la maison (1987) because their baby teeth were falling out. However, the director made an exception when the girls lost their two front teeth.

She donated many signed head-shots to Rocky Stone to be auctioned off to raise money to buy more toys for less fortunate kids as part of the Toy Mountain Campaign 2004.

Mary-Kate is younger than her twin sister Ashley by about two minutes.

Mary-Kate was supposed to play "April" in "Story of a Girl", but the movie has been put on hold. Sortilège (2011) was Mary-Kate's final acting project.

When she was young, she and Ashley used to call their La fête à la maison (1987) co-stars by their characters' names so they would not mess them up during taping.

Had a line of clothing with sister Ashley that was sold at Wal-Mart until 2006.

While making the film Sarah et Julie n'en font qu'à leur tête (1992) in Canada, she rode her first horse and became a devoted equestrian.

Has two horses, CD and Star, and has won several prizes with them.

On June 22, 2004, she has reportedly entered a program for treatment of an eating disorder.

On their 17th birthday (June 13, 2003), CNN announced not only their birthday, but their total financial worth - $150,000,000 for each of them. The same news source predicted the twins may be billionaires by the time they turn 21.

Older sister of Elizabeth Olsen. Younger sister of Trent Olsen. Has a younger half-sister, Taylor Olsen, and a younger half-brother, Jake Olsen.

Majors in Cuisine at New York University.

In 2004, her wealth was estimated at $137 million.

She is of Danish and Norwegian descent.

Mary-Kate is shorter than her twin sister Ashley by one inch.

She and her twin sister, Ashley Olsen, received a star on the Hollywood Walk of Fame at 6801 Hollywood Boulevard in Hollywood, California on April 29, 2004.

Her film Une journée à New York (2004) earned only $5.96 million during its opening weekend. This was the lowest amount ever earned for any film opening in over 3,000 theaters. The record was later surpassed by Hoot (2006), which earned just $3,368,197 at 3,018 theaters in 2006.

Her favorite movie from 1986 is Labyrinthe (1986).

In 1993, she and Ashley were supposed to play young Eves (Teena and Cindy) on X-Files : Aux frontières du réel (1993), but were eventually replaced by the Krievins twins (Erika Krievins and Sabrina Krievins) from the nearby city of Vancouver. The reason was very strict child labor laws.

Mentioned in the song "High School Never Ends" by Bowling for Soup.

Had a bi-monthly magazine called "Mary-Kate and Ashley Magazine" that only ran for three issues.

Her favorite band is Dave Matthews

With her sister, Ashley Olsen, attended school with Briana Evigan.

She helped in raising 2,206 toys for the Less Fortunate Kids as part of the 2005 Toy Mountain Campaign with Kids Talent Agent Rocky Stone. (December 2005)

Her friends used to travel with her and her sister, Ashley Olsen, to their filming locations. Their friends had also been extras in their movies before, a cafeteria scene in Tel père... telles filles (1999) and a scene in Liées par le secret (2000) that was filmed in Los Angeles.

Mentioned with her twin sister, Ashley Olsen, in Jay-Z's and Ye's song, "Paris".

She and her sister Ashley were both ranked #6 in E's 50 cutest child stars all grown-up (2005).

Mary-Kate and Ashley currently manage four clothing lines called "The Row", "Elizabeth and James", "Olsenboye" and "StyleMint".

During 8th grade, the only class she and her sister, Ashley Olsen had together was French and it was their first year taking a foreign language.

Her favorite party song is "Rock Your Body".

Hospitalized on November 19, 2007 in New York for a kidney infection.

She and her twin sister Ashley Olsen are yet the only regulars of La fête à la maison (1987) not to appear on its revival La Fête à la maison: 20 ans après (2016).

She and Ashley Olsen attended Aaron Carter's 13th birthday party. In addition, the singer said that if he was to pick any famous girl to date, it would be Mary-Kate Olsen.

Learned the 8 dances for her and her sister, Ashley Olsen's, "Dance Party" CD-ROM in only 2-3 hours.

Hardly ever fights with her sister Ashley Olsen, but the times they fight is usually over clothes.

At age 17, she and her twin sister Ashley were rated 2003's second hottest teen female stars.

Voted the 20th most wanted young star for the new year by Access Hollywood (1996) and The-N networks. Her twin sister Ashley wasn't part of the honor.

She and Ashley Olsen were Teen Ambassadors for the 1999 Women's World Cup Soccer.

Ranked #3 in VH1's list of the "100 Greatest Kid Stars" with sister Ashley

She and her sister, Ashley Olsen, dedicated the Holland-America Line cruise ship, the "MS Zaandam". (May 2000)

Parents are David Olsen and Jarnette Olsen (divorced).

Has a nephew Otto Eisner (b. 2023) via sister Ashley Olsen and brother-in-law Louis Eisner.