Doctor Who is a British science fiction adventure program produced by the BBC since 1963. It has consistently boasted engaging characters, weird situations, strange aliens, and memorable villains. It often engages with complex or nuanced themes such as the nature of humanity, good versus evil, ecological waste, and many others.
The series centers on a nigh-omnipotent alien being called simply the Doctor. The Doctor is a Time Lord, an alien species who has mastered interstellar, interdimensional, and time travel. The Doctor almost always chooses for himself at least one human companion from contemporary Earth who acts as the viewpoint character for the audience through increasingly strange adventures.
The Doctor and his companion travel in the TARDIS, a space and timeship that allows them to visit anywhere and anywhen. This allows the show to act as something of a genre engine, sometimes being about science fiction themes, sometimes facing historical crises, and sometimes simply having a weird fantasy world to play in.
In addition to the constantly shifting backdrop and rotating cast of human companions keeping the show fresh, the Doctor can also change. When a Time Lord dies, he regenerates into an almost entirely different person with the memories and knowledge of his predecessors, but a radically different personality.
This allows different actors the opportunity to play the Doctor over the span of the show. With the opportunity to tell stories set across all of time and space with a rotating cast of main characters, the show has championed diversity and storytelling in a way few other series could.
Doctor Who is a classic of science fiction television that shows no signs of slowing down as it continues into the future.