The SIDRAT is an interdimensional time machine. The exact opposite of the TARDIS, it has some unique abilities. It is larger on the outside then on the inside. Although varying in shape and size, a small version's outside would resemble a European crime ring, however the inside is about the size of a front toilet situated in a small cottage in middle England. The house is actually quite lovely, it has two cats, a greenhouse in the garden, including some rare species of orchids and an intercomm system. SIDRAT is believed to stand for Superb Intelligently Designed Radio-Active Toast.
The SIDRAT's most interesting feature is that it in fact stands still in time and space, and therefore only existed for a single moment in the history of the universe. It is therefore very rare, has never been sighted, except by exceptionally gifted people, and thus is an unusual delicacy available in some rather more upmarket Japanese restaurants. Details of the restaurants in question can be given at request - That last sentence is brought to you in association with Hwangaki & Associates Quality Restaurants and Assorted Delicacy Manufacturers.
The origins of the SIDRAT are never entirely clear. Some say that they where built by the Time Lords in order to counterbalance the massive power of the TARDIS and to minimise its effect on the universe. As the TARDIS feeds off the universe for its power, the SIDRAT feeds its power directly into the universe. Although this is probably the most likely explanation, seeing as how a device that exists for a single blip on the face of time and the universe has limited use for anything else, other explanations include that the SIDRATs where built as marker points in time and space, and some, more logical trains of thought place the blame for the SIDRATs existence on sheer boredom on the part of the Time Lords. SIDRATs have also been rumoured to have been used as the first ever closet.
Although sightings of the SIDRAT are very rare, due to its infinitely non-existent nature, their presence can be detected thanks to a few tell tale signs. These signs include, to name a few, spontaneous nuclear explosions as your atoms attempt to be in the same place as a newly built SIDRAT, Suddenly walking into an object that is invisible a moment after, and the old favourite, the least beautiful sound in the universe.