It's a dull job, but someone's got to do it. Mafalda Hopkirk worked for the Ministry of Magic, or "the fun police" as we like to call them. Basically, if you did something using your magic powers which you weren't really supposed to do, you'd be receiving a strongly worded letter from Mafalda. Harry can count himself among her list of recipients because of the aforementioned 'inflating Marge' accident.
The well-known and kind-hearted actor Sophie Thompson took on the part, which must have gone against her nature. An Olivier award winner, she first came to major prominence as Lydia in "Four Weddings and a Funeral" in the 1990s. Away from her work, she's a committed supporter of charities. She has run marathons in support of children suffering with disabilities and learning difficulties in London, and also for people suffering the long-term effects of serious burns. A gifted cook and author, she's released recipe books and children's books, too!