My marauder mug!
When you put hot water or milk in it, it turns white with the mischief managed and then that fades away as it cools down.
can be brought from - http://www.wbshop.com/Harry-Potter-I-Solemnly-SwearMischief-Managed-Transforming-Mug/HPNCMUGS,default,pd.html
Note to self: Buy this for Kuro
Dusty you need this.