Jack Harkness

Captain Jack Harkness
Doctor Who character
First appearance	"The Empty Child" (2005)
Last appearance	"The Blood Line" (2011)
Portrayed by	John Barrowman
Information
Affiliated	Time Agency Ninth Doctor Tenth Doctor Torchwood Institute
Home era	51st century

Captain Jack Harkness is a fictional character played by John Barrowman in Doctor Who and its spin-off series, Torchwood. The character first appears in the 2005 Doctor Who episode "The Empty Child" and subsequently features in the remaining episodes of the 2005 series as a companion to the series' protagonist, the Doctor. Subsequent to this, Jack became the central character in the adult-themed Torchwood, which aired from 2006 to 2011. Barrowman also reprised the role for guest appearances in Doctor Who in its 2007 series and 2008 series, as well as the two part special The End of Time.

In contrast to the Doctor, Jack is more of a conventional action hero, as well as outwardly flirtatious and capable of acts which the Doctor would view as less than noble. In the programme's narrative, Jack begins as a time traveller and former con man from the 51st century, who comes to travel with the Ninth Doctor (Christopher Eccleston) and his companion Rose (Billie Piper). As a consequence of his death and resurrection in the 2005 Doctor Who finale, Jack becomes immortal and is stranded on 19th century Earth. There he becomes a member of Torchwood, a British organization dedicated to combating alien threats. He spends over a century waiting to reunite with the Doctor, over which time he becomes Torchwood's leader. Eventually, he reunites with the Tenth Doctor (David Tennant) for several appearances in Doctor Who. Aspects of the character's backstory—both prior to meeting the Doctor, and during his many decades living on Earth—are gradually revealed over Torchwood (and to a lesser extent, Doctor Who) through the use of flashback scenes and expository dialogue.

...
Wikipedia