Mary Willow Batson Bromfield aka Mary Marvel is one of the supporting protagonists in Batman: The Brave and the Bold.
She is voiced by Tara Strong.
Mary was twin sister of Billy and the daughter of C.C. and Marilyn Batson. Technically, she is three seconds older than Billy. When their parents were killed on an archaeological dig, Mary and Billy were split up. Each carried half of a locket given to them by their mother. Mary also kept a doll from their childhood, Mister Tawky Tawny. She was adopted by the rich couple, Mr. and Mrs. Bromfield. Thanks to Batman, the twins were reunited with each other and Batson had the family he always yearned for.
Mary Bromfield was soon given powers, too, and became Mary Marvel. Together with Captain Marvel, she helped to save the life of their friend, Freddy Freeman by giving him powers, too. Soon, the Marvel Family was formed and Fawcett City was kept safe by a close-knit unit of superheroes. However, Mr. Mind used his thought control to manipulate the team into disbanding. Luckily, Batman made them realize the error of their ways and they arrived to help him defeat Mr. Mind. In the aftermath, Mary Marvel admitted she thought a Batbaby was cute.