Prank your sister with this hilarious color changing coffee mug. One side shows World's Best Sister, while the other side reads World's Worst Sister.
Is your sister left or right handed? Choose which hand your sister holds her mug in so that the prank can work to its full effect.
· Heat activated, color changing mug
· Starts out black and changes color in 15-30 seconds when a hot beverage is added
· Available in 11 oz size
· Machine washable