Harriet Pratt was a small-time con artist and occasional escort. She was eventually recruited into The Wonderland Gang by Tweedledee and Tweedledum.
March Harriet was created by Paul Dini and Dustin Nguyen and first appeared in Detective Comics #841.
As a member of the Wonderland Gang, March Harriet participated in an robbery during Gotham Fashion Week. The Gang fled when police arrived, but robbed Empire Bank the next morning. Batman tracked the Wonderland Gang to Gotham's Amusement Mile, an amusement park. March Harriet ambushed Batman alongside her teammates in the Hall of Mirrors, but was quickly defeated and taken into custody.
Batman: Arkham City
March Harriet appears briefly in the comic based on the video game series. Vicki Vale, Catwoman, and Poison Ivy were captured by the Wonderland Gang. Batman tracked the gang back to the Mad Hatter's Hat Shop, where March Harriet greeted the hero. She told him he doesn't belong there, and sends the Lion, the Walrus, and the Unicorn after him. Batman defeats the three, then knocks Harriet out by throwing her into the Unicorn.
Batman: Li'l Gotham
March Harriet appears alongside The Wonderland Gang in the Li'l Gotham universe. She attended a tea party with the captured Batman and Robin, and later attacked Batman, though she was quickly defeated.
Lego Batman Movie
March Harriet appears in the movie, with no speaking lines, as one of the Batman villains.