Sour Susan is a girl who attends Ashton Primary School. She is notable for being Moody Margaret's best friend. She likes to copy Margaret when she insults people such as Horrid Henry, Rude Ralph or even Perfect Peter. That is why many Horrid Henry Fans find Susan irritating. She does have arguments with Moody Margaret, such as in the episode Horrid Henry and the Football Fiend, where she tries to ask Moody Margaret who she was going to take to the Ashton Athletics match, and Moody Margaret gave her the reply that she will take Susan but in an annoyed voice. Susan always moans at Margaret and Henry. Sometimes, she is enemies with Moody Margaret like mentioned in Horrid Henry And The Secret Club.
Susan appears to have curly ginger coloured hair and pale skin. She usually wears a lime coloured dress, with green sneakers. Her face is mostly puckered.
- She has a younger sister known as Vicious Vicky who likes biting people.