Professor McGonagall: "Harry Potter! Thank goodness you`re here! There`s been an accident; a candle has been changed into a rabbit."
Harry: "That certainly sounds like an accident."
Professor McGonagall: "It was a lit candle… and it escaped! I`m afraid it might set fires. I need someone to catch it. And I`m assigning you."
Harry: "How will I know the rabbit when I see it?"
Professor McGonagall: "It`s purple. That`s unusual, even at Hogwarts."
Professor McGonagall conversing with Harry Potter in 1991[src]

The Purple Rabbit (known also as a Flaming Purple Rabbit) was a beast created by the accidental Transfiguration of a lit candle in September of 1991 at Hogwarts School of Witchcraft and Wizardry. Before anyone in the Transfiguration class in which it had been produced could stop it, the beast escaped into the grounds. Professor Minerva McGonagall informed Harry Potter of the accident and entrusted him with the capture of the oddity lest it accidentally burn things. He was awarded twenty-five house points for retrieving the rabbit.