Never “Doctor Who”. Just the Doctor.
A Time Lord from the planet Gallifrey who stole a time machine, the TARDIS (“Time And Relative Dimension In Space”): bigger on the inside, stuck looking like a 1960s British police box because its disguise circuit broke. When dying, the Doctor regenerates: new body, new face, new personality. That’s the trick that has let Doctor Who change its lead actor and survive for sixty years.
So far, fifteen numbered Doctors: William Hartnell, Patrick Troughton, Jon Pertwee, Tom Baker, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann, Christopher Eccleston, David Tennant (tenth, and fourteenth too), Matt Smith, Peter Capaldi, Jodie Whittaker (the first woman) and Ncuti Gatwa (the first Black lead), plus a few unnumbered ones.
The Doctor rarely travels alone: the companions are our eyes. Rose Tyler is the best-known of the modern era, and River Song the most complicated love story (A love story told backwards). Archenemies: the Daleks.