Doctor Who is a fictional TV series that had been running in the UK since the 1960s. It features the extraterrestrial Doctor, who time travels across the Universe. The Doctor lives and travels in the TARDIS, which appears from the outside as a blue police box, but inside it is much bigger. The Doctor appears in many physical forms, due to the fictional device of regeneration whereby the Doctor can transform when their current body is too damaged to heal. The Doctor has always been a man, but has recently regenerated into a female form. She is the first female Doctor, and she is great.