The sales 'patter' from the bottom of the Tardis Mug includes:
Link: ThinkGeek :: TARDIS MugQuote:
- 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.