Fourth Doctor

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. After his regeneration, 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 the Giant Robot. But he rarely returned to UNIT during this incarnation, although he often visited Earth in the twentieth century.

He returned to Gallifrey on at least two occasions. The White Guardian sent him on a quest to locate and assemble the pieces of the Key to Time.

After the destruction of Logopolis, he fell off a radio telescope; a mysterious entity known as the Watcher, which had been following him for some time, then merged with him, spurring on his next regeneration.