The Fifth Doctor was far more human in his demeanour than any of his previous regenerations. This was not a Doctor who was prone to peculiar mannerisms -- instead, he often behaved just like a regular man, even in his less paternal, more turbulent and argumentative relationship with his companions. Enthusiastic and spritely, this Doctor demonstrated a notably more fallible outlook than in the past: he could make mistakes, and sometimes the cost of these errors was very high indeed. The years were beginning to tell upon the Fifth Doctor, as they had during the latter days of his fourth incarnation; he was being who had seen and endured much, both good and bad. Despite his boyish appearance, there could be little doubt that, at his core, the Fifth Doctor was a very old man.

Peter Davison played the Doctor from Logopolis in March 1981 to The Caves Of Androzani in March 1984. He returned for Dimensions In Time in November 1993.

Vizlor Turlough was an enigma. His history was never made clear until the end of his time with the Doctor, and his motivations were always his own. Generally speaking, Turlough served himself first and foremost and his companions only when it was to his mutual advantage. But during his travels, he began to learn the value of friendship and cooperation -- it was a far wiser, less selfish Turlough who eventually left the TARDIS. A resourceful person, it would not be beyond Turlough to go to any lengths to accomplish his goals. He possessed a keen instinct for survival and a sharp intellect, which as often as not aided his friends as much as himself.

Mark Strickson played Turlough from Mawdryn Undead in February 1983 to Planet Of Fire in March 1984. He returned as a regenerative image for The Caves Of Androzani in March 1984.

Like K-9 before it, Kamelion was an artificial intelligence. A robot able to shift shapes at the whim of its controlling master, Kamelion's default form was humanoid. Its personality was equally malleable. Despite some indication of self-awareness and a desire to assist the Doctor, Kamelion sadly proved so weak-willed as to be susceptible to any nearby dominant personality. Forever a pawn and never a player, Kamelion could never hope to be as helpful to the Doctor as its mechanical predecessor.

Kamelion appeared in The King's Demons in March 1983 and Planet Of Fire in February and March 1984, and as a regenerative image in The Caves Of Androzani in March 1984. Its default voice was provided by Gerald Flood.

American Perpugilliam Brown, or "Peri" for short, was ostensibly a botany student, although she rarely showed any interest in the subject. Making up for her lack of maturity with a surfeit of stubbornness, it is little wonder that she and the equally obstinate Sixth Doctor had such a hard time getting along. Nevertheless, Peri also proved to be a tender and charismatic individual, and the evolution of her relationship with the Doctor, from its acrimonious beginnings to a mixture of knowing sarcasm and genuine respect, demonstrated that she was well on her way to becoming a mature and well-rounded adult.

Nicola Bryant played Peri from Planet Of Fire in February 1984 to The Trial Of A Time Lord in October 1986. She returned for Dimensions In Time in November 1993.