Captain Jack Harkness

Captain Jack Harkness is a supporting character in the BBC television series Doctor Who, appearing as a companion of The Doctor on several occasions. He is also the lead character in the spin-off series Torchwood.

Personality
Jack Harkness' personality was willfully enigmatic. He enjoyed his persona of 'mysterious time traveller,' much of which remained constant in his experiences with Torchwood and the Doctor. Before being cursed with immortality, he was a flippant former con man who loved adventuring with the Doctor and seducing beings throughout the universe. Jack automatically flirted with most people he met, not caring about their gender or if they were human, alien or even robots. The Doctor often told him to stop and Jack would often reply, "I'm just saying hello". But as the Doctor pointed out, "For you, that's flirting". From this, it can be inferred that Jack is an omnisexual.

Besides being a flirt, Jack was a drinker. He once remarked that on one occasion when he was sentenced to death, he got drunk and ended up in bed with both his executioners. He told Rose that he preferred to discuss business while he was drinking. Jack claimed to the Ninth Doctor that before he met him he had been a coward and said that he might have been better off that way.

Despite the fact that he was incapable of dying even if he wanted to, Jack retained a sense of humour, frequently telling jokes and being lively and cheerful. However, underneath his cheerful demeanour, Jack was unsure if he wanted to die or not. Living forever (or at least as near to forever as a human could live) brought him to an existential viewpoint. While he joked about grey hairs and remained silent about mortality, Jack saw death as the ultimate end of being; there was no afterlife and no one waiting for him from his past lives. Although friendly and flirtatious, Jack could also be ruthless at times and did not hesitate to kill anyone or anything that he felt was a threat. This sometimes got him into trouble with his allies in Torchwood who disapproved of his lack of compassion. On one occasion Owen Harper shot him because he felt that Jack didn't care about what they had lost. Although he could be aggressive, Jack still cared deeply about his allies and was devastated when any of them were harmed or killed.

Always a vocal, unreliable narrator of his own adventures, Jack was as much of a mystery to the people he met as the countless lives he claimed to have led. Jack continued to protect himself with an air of mystery. No one he encountered knew his real name or many details about his career or life. He often told anecdotes about his sex life, but no one knew how many were real. Though he professed "responsibility" as his motto after the Year That Never Was, the utter devastation Jack experienced in the space of five days over the course of the 456 incident and the deaths of his grandson and Ianto Jones left him wracked with guilt and grief, unable to remain on Earth. When he returned to Earth, Jack seemed to be a shadow of his old self because he had lost so many people he cared about, although he had recovered enough to stay on Earth in order to defend it.

Jack was haunted by the loss of his younger brother Gray and spent many decades searching for him. He blamed himself for Gray's disappearance because he'd let go of his hand when they were fleeing from aliens during their childhood. Jack loved his brother deeply and, even after Gray turned against him, Jack told him that he forgave him.