Short answers, pulled from the story.
The first episode of Doctor Who aired on the 23rd of November 1963. This broadcast occurred exactly eighty seconds after the scheduled time due to extended news coverage of the assassination of John F. Kennedy.
The Daleks were created by writer Terry Nation and designed by Raymond Cusick. Their debut in the second serial The Daleks in 1963 brought viewing figures between 9 and 14 million.
The serial The Deadly Assassin in 1976 established that a Time Lord could only regenerate twelve times for a total of thirteen incarnations. The episode The Time of the Doctor in 2013 resolved this limit by depicting the Doctor acquiring a new cycle of regenerations.
The Doctor Who theme music was composed by Ron Grainer and realized by Delia Derbyshire of the BBC Radiophonic Workshop. Derbyshire created the arrangement by cutting, splicing, speeding up, and slowing down segments of analog tape.
97 of 253 episodes produced during the programme's first six years are not held in the BBC's archives. These missing episodes include many from the eras of the first two Doctors William Hartnell and Patrick Troughton.
Jodie Whittaker became the first woman to play the Doctor in 2017. Ncuti Gatwa subsequently became the first black actor to headline the series in 2023.