Wissenswertes

Her special Academy Award as Outstanding Juvenile Performer for Heimweh nach St. Louis (1944) was stolen and she was unable to regain it for nearly fifty years when two memorabilia collectors came across it at a swap meet and managed to give it back to O'Brien.

In a practice common among child actors at the time, O'Brien adopted as her professional first name the name of the character who was her first credited part in Journey for Margaret (1942).

Gave birth to her only child at age 39, a daughter Mara Tolene Thorsen, on July 12, 1976. Child's father is her second husband, Roy T. Thorsen.

Stated on Turner Classic Movie's Child Stars (2006), that she is half Spanish.

In April 2006 she was presented with one of the first two Lifetime Achievement Awards ever awarded by the SunDeis Film Festival at Brandeis University. Celeste Holm received the other.

For her role as "Beth" in Kleine tapfere Jo (1949), she worked again with Mary Astor, who played her mother "Marmee", and also played her mother in Heimweh nach St. Louis (1944). In this film, she also worked again with Harry Davenport, who played "Dr. Barnes" and who played her grandfather in Heimweh nach St. Louis (1944), and also with June Allyson, who had already played her sister in Musik für Millionen (1944).

Received the Women's International Center (WIC) Living Legacy Award. (1996)

In 1959, Ms. O'Brien starred in a national stage tour of "The Young And The Beautiful" by author Sally Benson (creator of the book that became O'Brien's most famous film, Heimweh nach St. Louis (1944)). Co-starring opposite O'Brien in the stage play of "The Young And The Beautiful" was Dirk Wayne Summers, who later became an award winning writer and director in films and television.

Was suggested for the role of Emmeline as a child in Die blaue Lagune (1949) but an agreement between MGM, the company where she was under contract, and Rank, the company that financed the project, could not be reached.

Began wearing a nose ring in 2010.

In Italy, almost all of her films were dubbed by Loredana Randisi.

In 1949 Margaret was announced for the voice of Alice in the upcoming Walt Disney animated production of Alice im Wunderland (1951), but details could not be worked out, and the voice of Alice was provided by Kathryn Beaumont.