Irma is Bianca Castafiore's maid. She accompanies Madame Castafiore all over the world during her singing tours.
Irma first appears in The Calculus Affair. In The Castafiore Emerald, she accompanies Castafiore and her pianist Igor Wagner to Marlinspike Hall. Later, Irma's gold scissors go missing and are found by the police in Miarka's possession. Miarka said she found them under a tall tree, leading Tintin to solve the mystery of the thieving magpie. In Tintin and the Picaros, Irma, Wagner and Castafiore are wrongly imprisoned in San Theodoros. They are freed by Tintin and Haddock when General Alcazar takes back power from his rival General Tapioca.
Castafiore describes Irma as a faithful, loyal and honest servant. Despite giving a meek impression, Irma has a strong sense of personal pride: when Thompson and Thomson accuse Irma of stealing Castafiore's emerald, she becomes very angry and assaults them with one of the pair's walking sticks.