Doctor Who has always had such a recognizable theme song, there has also been quite a few "good" knockoffs of the song. Nothing better than Jon Pertwee singing about being the Doctor. Classic.
Then there was The Timeloards/KLF with Doctorin' The Tardis. Dig the 1968 Ford Galaxy.
Doctor Who - Original Television Soundtrack
Doctor Who
Doctorin' the Tardis
Doctorin' The Tardis / What Time Is Love?
