HARRY POTTER Heat Changing Mug - Marauder's Map. Officially licensed merchandise. This Harry Potter mug is an absolute must-have for every fan of the world of witchcraft and wizardry. Cold, the mug shows the password to the famous Marauder's Map - "I solemnly swear that I am up to no good" - and some footprints indicating the students and teachers of Hogwarts walking around the school. When hot liquid is poured in, the mug transforms to reveal Moony, Wormtail, Padfoot & Prong's Marauder's Map. Once the drink is finished, the password to close the map - "Mischief Managed" - is revealed at the bottom and the mug returns to its original state as it cools. A perfect gift choice for a true Harry Potter fan.