12. A time-travelling alien (who often visits Earth) picks up companions along the way as he goes about in his time machine that is shaped like a 1960's-era British police call box.
From Quiz Match the TV Plots - Over 20 Season-Long Shows
Answer:
Doctor Who
With seven actors who played the main character, the plot device was added that when a Time Lord was about to die, he could regenerate (up to 12 times), looking and acting quite a bit different. (1963-1989)
"Doctor Who" has been revived in a second series, begun in 2005. It has continued with the continuity of the original series, with the ninth, tenth, and eleventh Doctors, portrayed by Christopher Eccleston, David Tennant, and Matt Smith. (The eighth Doctor, played by Paul McGann, was only portrayed on-screen in the 1996 made-for-TV movie.)