Fitz Kreiner

Fitz Kreiner was a companion of the Eighth Doctor.

The "original" Fitz
Fitz Kreiner was born to Otto Kreiner and Muriel Kreiner in 1936. Before meeting the Doctor and Sam, he worked in a florist’s shop and lived in a small third floor flat in Archway. Fitz was an excellent guitarist. He performed under the name Fitz Fortune to avoid calling attention to his German heritage. (EDA: The Taint)

When the Doctor, Sam and Fitz landed on Earth in 1996, three or four distinct iterations of Fitz Kreiner were brought into existence. Fitz was placed in The Cold by the United Nations in 1996 in Geneva and removed from it in 2593 on Ordifica. Fitz decided since he was so far from the Doctor and his own time, he would become an agent of Faction Paradox. (EDA: Interference - Book One)

On joining the Faction Paradox, Fitz and the other survivors of Ordifica were taken back in time. They were placed on Anathema by the Faction Paradox to become their troops, the Remote. Fitz joined their society without actually becoming a part of it in the literal sense. While on Anathema, he contemplated suicide. He joined the Faction Paradox and was indoctrinated into its ranks.

Before leaving Anathema, Fitz placed his memories in a Remembrance Tank. It moulded a replica of him out of Biomass so his memories and personality would live on in the Anathema. Fitz, or rather the re-remembered version of Fitz, lived on Anathema for over five hundred years on their journey towards Earth. The re-remembered version of Fitz became Kode, who came to Earth selling the Cold with Compassion and Guest.

The Doctor recognised elements of Fitz’s personality in Kode and offered to use the TARDIS’s telepathic circuits to re-remember Kode as the Fitz who had joined the Doctor in 1963 and as the man he had been when the TARDIS had lost contact with him. (EDA: Interference - Book Two)

Following his Re-Remembering
Fitz travelled with the Doctor and Compassion to Gallifrey, where he tried to prevent Faction Paradox from invading. Gallifrey was destroyed by the Doctor and Fitz was picked up by Compassion and deposited on Earth to meet the Doctor in 2001. (EDA: The Ancestor Cell, Escape Velocity)

Fitz once claimed that between the Doctor and him, Fitz was the real hero. He did this while trying to collapse the corrupt Alien Defense Incorporated. (BFA: Fitz's Story)

Some of Fitz's memory after the destruction of Gallifrey had been destroyed, but to a far lesser degree than the Doctor's. (EDA: Escape Velocity) Fitz soon regained his memories but never told the Doctor; the Doctor wanted to move on from his previous life. (EDA: Halflife) Fitz developed a relationship with fellow companion Trix and planned to leave the Doctor after the Vore were defeated. (EDA: The Gallifrey Chronicles)

At some point after leaving the Doctor, Fitz was recruited by Iris Wildthyme to help negate a timeline created by Spiritus Mundi. (OBIW: Only Living Girls)

Pre-Re-Remembering
Fitz thought most people stupid and would tell tall tales like  J. R. R. Tolkien having been born between 'R.J Tolkien' and a prostitute called Frodo.

When Sam had been attacked and was unconscious, Fitz brought her safely back to his home. He also stole her money, intending to claim her attackers had stolen it. (EDA: The Taint)

Fitz suffered from a bit of the 'comic book' syndrome; he thought that he was special only if someone noticed. (EDA: Demontage)

He also liked to play the character of various fictional characters from movies and novels, such as James Bond. (EDA: Revolution Man)

Fitz slept with a dark haired Samantha Jones. (EDA: Unnatural History)

Post-Re-Remembering
After re-remembering by the TARDIS, Fitz seemed more at ease with himself, more attuned to the ways of the TARDIS and travelling through time.

Fitz enjoyed tea, and sorely missed the TARDIS's supply of tea when it was thought to be destroyed in the dimensional barriers between Avalon and Earth. (EDA: The Fall of Yquatine)

Following the Doctor's hundred years trapped on Earth, Fitz knew more about the TARDIS and the Doctor's life than the Doctor himself. He demonstrated an affinity with the TARDIS in keeping things (such as the Doctor's memories) from the Doctor. (EDA: Escape Velocity, EarthWorld, Trading Futures)

He had an affinity for forming friendships, first with Sam and then the Doctor, and later (although they were reluctant to admit it) Compassion and Anji.

Over time he developed a number of Doctorish traits, such as taking the lead in investigations into the unknown and taking great pride in providing expert commentary, as well as a love of travel.

He described the Doctor as being a pain, but admitted missing him when he wasn't there. Fitz did not completely trust the Doctor, believing that he could have stolen the body of Richard Harries from Banquo Manor. (DW: The Banquo Legacy)

Appearance and habits
Fitz donned a leopardskin suit with snakeskin shoes whilst in Las Vegas. (EDA: Mad Dogs and Englishmen) He once wore a wide-brimmed hat like the Doctor. (EDA: Camera Obscura)

Fitz smoked a lot of cigarettes, and drank just as much. (EDA: The Gallifrey Chronicles)