Madge Undersee is an important minor character in The Hunger Games and Catching Fire but she doesn't appear in the films at all. She is the daughter of the mayor of District 12 (our heroes' district) and had been Katniss' best female friend since childhood. She and Katniss grow even closer in Catching Fire and she uses her relative power and wealth to assist Katniss and Gale. But most significantly, she gives Katniss the mockingjay pin that would come to be the symbol of the revolution. The movies have Katniss receiving it from Greasy Sae, an elderly local merchant, which robs it of some of its emotional significance. It also means we lose the touching moment when Katniss finds out about Madge's death.