Many of their games are included in the books about Madicken (Mardie in the English translation) and Lisabet. Madicken was brave, strong, and daring, and she taught Astrid how to fight. Like Astrid, she enjoyed climbing high into trees and onto roofs. Lisabet, Madicken's fun and imaginative little sister, had many similarities to Astrid's younger sister Stina.

There was a girl in Astrid's school who had stolen money from a coat pocket and bought candy with it. As punishment, she was beaten in front of the whole class. This story stayed in Astrid's memory and later appeared in one of the Madicken books when her classmate Mia gets beaten. In both the movie and in the book, it's a powerful scene – Madicken's scream, her NO! NO! NO! that makes us understand the meaning of the abuse and violence that Astrid Lindgren protested against in both her life and her writing.

The Madicken in the books is inspired by the real Madicken but of course also by Astrid herself. Anne-Marie Ingeström (later Fries) was Astrid's best friend for almost 80 years. Astrid Lindgren didn't reveal that Madicken existed in reality until after Anne-Marie's death in 1991. "It was an agreement they had: there could be a risk that my mother's friend would attract attention, and she didn't want that," Astrid's daughter Karin Nyman has revealed.