The TARDIS - Time and Relative Dimensions In Space - is the Doctor's mode of transport. It is a time machine, and can craftily disguise itself to match the surroundings where it lands. Much to the delight of the BBC’'s accountants, the TARDIS got stuck as a Metropolitan Police Box in a junk yard in London, and save for a couple of changes, it has never recovered. Afore mentioned accountants could sleep easily in their beds, safe in the knowledge that when the TARDIS lands in another time or place, it won’t need a re-design.

In fact, the TARDIS has changed shape and dimensions slightly, with the current Eccleston/Tennant model being a little fatter than its predecessors.

The two examples here are to scale. The large one is a money box, which when you open the doors says something about most planets having a north. Closing the doors results in the light on top flashing, and the familiar dematerialisation noises. I suspect that my money is being sent to the BBC covertly…

The smaller TARDIS is a mobile phone ringer. It kind of knows that your mobile phone will ring, and will make TARDIS noises before the phone goes off. I think it travels in time to work this out.