Doctor Who: 10 Things Everyone Always Gets Wrong About The TARDIS
1. There's Only One Type Of TARDIS
In the very first episode of Doctor Who, Susan claims that she named the TARDIS, and that she came up with the acronym Time and Relative Dimension in Space.
However, there is evidence that the term was well-known on Gallifrey before the First Doctor departed. Additionally, people who never met Susan - such as the War Chief and Lord President Borusa - are all familiar with the term. Plus, Bill Potts also noted that the acronym would only work in English.
The term might be widely known because there are actually 160 different types of TARDIS. The Doctor’s TARDIS is a Type 40, and is actually considered old and obsolete by many Time Lords the Doctor encounters. Type 1 TARDISes are considered the most dangerous - they were difficult to operate, and would often develop minds of their own and roam the universe.
Elsewhere, the Master had a Type 45 TARDIS with the ability to take control of other TARDISes, and the Monk had a Type 40 Mark IV, which was more advanced than the Doctor's.
The show has never properly explored these alternate TARDISes - hence why many people don't even know about them - but hopefully it will one day.