Fourth Doctor

Biography
Having regenerated, the Fourth Doctor, he seemed to be in a hurry to leave Earth, but was eventually persuaded to stay and help Brigadier Lethbridge-Stewart deal with Think Tank and their K1 robot. The Fourth Doctor took Sarah Jane Smith and Harry Sullivan to travel with him in the TARDIS. Harry decided to leave and Sarah Jane to continue on with him.

The Fourth Doctor rarely returned to UNIT during this incarnation, although he often visited Earth in the the 20th century.

Recieving a distress call from Gallifrey, he returned Sarah to Earth ("The Hand of Fear"), the Fourth Doctor travelled to his homeworld in order to defeat an unknown menace, in fact, the Master ("The Deadly Assassin"). The Doctor travelled for an unknown period of time alone. On a nameless jungle world, he made the acquaintance of Leela of the Sevateem ("The Face of Evil"), a native of that world, and, together, travelled with the former pet of Professor Marius, the dog-shaped robot known as K-9 ("The Invisible Enemy").

Returning once more to Gallifrey, the Fourth Doctor, posing as vainglorious and powermad, sought and attained the office for Lord President as part of a scheme to save his homeworld from an invasion force of two separate enemies, the Vardans and the Sontarans. Leela decided to remain on Gallifrey with Andred, a Gallifreyan in the Chancellory Guard and K-9. However, the Doctor left the Capitol with a duplicate K-9, Mark ii, in a crate ("The Invasion of Time").

After an indefinite period of wandering with K-9 Mark II, the White Guardian summoned the Doctor to initiate a quest to locate and assemble the segments of the Key to Time which would restore harmony in the universe. For this purpose, the White Guardian introduced him to a new companion, Romana ("The Ribos Operation"). After several adventures through time and space, the Doctor and Romana located, assembled and dissasembled the Key, and fleeing the wrath of the White Guardian's opposite, the Black Guardian, the Doctor installed a randomizer in the TARDIS console ("The Armageddon Factor").

Struggling with the Master, he fell off the Pharos Project radio telescope down the ground hundreds of feet below. The mysterious entity known as the Watcher, which had been tracked him through time and space, then merged with him and he regenerated.



Characteristics
The Fourth Doctor was something of a cross between Willy Wonka and the Mad Hatter, rarely without his signature scarf of incredible length. He was perhaps the most eccentric incarnation.

Mysteries and Discrepancies

 * The Fourth Doctor visited Leela's home planet, presumbably alone, encountered the supercomputer Xoanaon and inadvertantly installed in him a program copied from his own personality ("The Face of Evil"). We do not know at what time in the Fourth Doctor's life this event occured or the reason why, later, he would fail to remember his adventure. One popular theory for the amnesia explains that this adventure as happening very early in his life {"Robot"), at which point he still suffered from post-regenerative trauma.