Margaret Millicent Maudita Smythe or Moody Margaret is a character in the Horrid Henry books and TV Series. She is best known as Horrid Henry's classmate. Margaret forms the Secret Club in her back garden, in which consists of her friends, such as Sour Susan, and occasionally Gorgeous Gurinder and Lazy Linda, this club often rivals with Henry's Purple Hand Gang, with her and Henry living next door to each other. Margaret lives with her parents and no siblings have been mentioned, so it's likely she is an only child. Henry is her neighbour. She sometimes calls him Bogey Brain and other names just like Henry.
Margaret might have a crush on Henry, although it is unknown because in the episode where Henry bangs his head and sees a vision of the future, he is engaged to Margaret. Also in Perfect Peter's Revenge when she thinks Henry loves her, Margaret puts on make up and wants him to admit it. In " Horrid Henry's School Play" when Henry was supposed to kiss her, she was not hesitant about it at all unlike Henry and went in for it.
Margaret was originally going to be a boy called Moody Martin, but Francesca Simon's husband didn't approve and believing the character was too much like Horrid Henry and therefore Martin became a girl called Margaret.