* Dark blue and painted to be a perfect replica of a 1950’s British police box
* Internal volume is smaller than the external. It’s a mug, not a time machine.
* Lid to keep the essence of your TARDIS contained until you’re ready for it.
* Won’t blend in with other, inferior mugs – broken chameleon circuit and all that.
* Impervious to the Master materializing another TARDIS inside yours.
From the great ThinkGeek