My favorite companion is Sarah Jane Smith. Highly original choice, no? Sarah Jane is everyone’s favorite companion. At least I am honest.
Sarah Jane has had the longest history with the Doctor, serving as the companion for the Third and Fourth while joining in adventures with all the first five (technically speaking, at any rate, in The Five Doctors) and the Tenth. She will hook up with the Eleventh in an upcoming episode of The Sarah Jane Adventures.. So she has experienced about all the Whoverse has to offer.
While I imagine Wholigans do not want to admit it, Sarah Jane is clearly a Lois Lane homage--an investigative journalist who cannot help but get involved in the story herself. My youthful comics obsession never really extended to the Superman mythos, but I appreciate any respectable references in other media.
Did we not all have a crush on Elisabeth Sladen at one time or another? She still looks nice today.