(Please click through to Think Geek. They might be having a sale!)
You may suspect witchcraft and/or wizardry when you see your mug change colors, but no, this is a simple muggle trick that requires only science! You don't need to study for your OWLs to pull this one off. You only need a hot beverage of your choice, and you're a bonafide "magic user." Congrats!Feel like you're powerful wizard with just a hot beverage and the Magic Wand Heat Change Mug. The mug is all black with the Harry Potter logo when cold, and is lit up with magic wands and spells when hot...