The Doctor

"I am here as a conscience for my future selves, and in my spare time I tend to a little hobby of mine – but, of course, I have a lot of spare time now..." -First Doctor, Azumanga Who

The Doctor (real name unknown) is a Time Lord, and a very pivotal character in Daniel's stories.

Background
"I thought the Doctor was just a myth – the sort of thing which gets made into an educational children's show that only runs thirteen weeks." -Jocelin Matthews

The Doctor is a Time Lord; Time Lords were a race of beings who had more or less complete mastery over time, however merely preferred to watch history rather than assist those who were wrongly opposed. The Doctor (known as "Theta Sigma" or "Thete" during his days at the Academy and, much later during his travels with Dorothy "Ace" McShane, "Professor") strongly opposed this and, with his granddaughter Susan, stole borrowed an outdated Type 40 TARDIS and fled from Gallifrey.

The Doctor has had a very storied past; according to the "New Adventures" line of novels, concluding an arc stretching from the 1989 television season through the sixty NA books (known as The Cartmel Masterplan), the Doctor may be a reincarnation of a Time Lord known as "the Other", who worked alongside Rassilon and Omega many millenia ago.

Incarnations
The Doctor, like all Time Lords, has thirteen distinct incarnations. Time Lords can, in fact, live forever "barring accidents"; these "accidents" are situations in which, when the Time Lord is near death, the regeneration process begins changing their body and some aspects of their personality while retaining the memories of past incarnations. When a Time Lord is in his/her final incarnation, forcing a regeneration will lead to a rather painful death.

A notable example of a Time Lord in his last incarnation is Professor Chronotis (Shada): although his age was not stated, he notes that he had witnessed the introduction of the Type 40 TARDISes as a young boy in his first incarnation. In The Deadly Assassin, it was revealed that the Type 40 was rather outdated and long since discontinued.

As for the Doctor, every one of his regenerations has caused an ill effect – from thinking he was a completely different person (The Power of the Daleks) to memory loss (Enemy Within) to instability (The Christmas Invasion); the First Doctor, however, ended up becoming a sort of anomaly in the TARDIS Rose Garden and advised his other selves.

In Daniel's Canon
In the author's canon, the Doctor's life has remained mostly the same as seen on television and in the spin-off media. When Azumanga Who was first published on May 24, 2008, the United Kingdom was still broadcasting Series 4 and no announcements had yet been made regarding the Doctor.

Tenth Doctor (Rich Karley)
The Tenth Doctor's life differed in a few ways, most notably appearance and voice...although this only seems to be when the Doctor himself tries to remember that period. The timeline diverges at An Insignificant Choice.

Eleventh Doctor (Ronald Howard)
At some point following the Doctor's regeneration (The End of Time), he settled down in Victorian London and became Sherlock Holmes. After supposedly dying over the waterfall, he planned to leave in his TARDIS...but John Watson discovered and subsequently joined him.

Among the adventures they shared were several that were much like Arthur Conan Doyle's subsequent books. Watson continued to write, but greatly simplified what happened because "my family would rightfully think I was rather mad".

This incarnation's final adventure was, rather appropriately, The Final Problem.

Twelfth Doctor (Jonathan Gundrie)
The new Doctor could be best described as "a pub rumbler after his favorite soccer football team lost", being far more brash than his predecessors and even going so far as to headbutt Daleks. Watson left shortly afterward, unable to cope with what he considered "the irrational behaviors of a lunatic".

The rest of this incarnation's life is unknown, although it is known to have ended after he charged into battle while having the Hypothematic Flu (Death To The Doctor!).

Thirteenth Doctor (Hugh Laurie)
The Doctor became far more sarcastic, taking on a persona not unlike Laurie's other famous doctor (Gregory House). Following the events of The Ogron Escapade, he took two orphaned companions who would turn out to be his last.

Following the destruction of a Cyberman base two years later, the Doctor was ambushed by a lone Cyberman and killed at point-blank range (Conversion of the Cybermen). House: The Dream gives his fate.

Fourteenth Doctor (Christine Hoez)
This incarnation lived for just one year, growing cold and bitter at her role to the point where Daniel was nearly locked out of the TARDIS several times. She died in Stronghold of the Daleks.

Fifteenth Doctor (Daniel Benfield)
By the time Daniel meets his first incarnation, still in the Rose Garden, said incarnation has become even more of an anomaly than before.

Sixteenth Doctor (Hannah Benfield)
As seen in Azumanga Who, Hannah is the Doctor whenever Daniel is in parts unknown. Thanks to the ring the First Doctor gave him, Daniel was able to regenerate into her after Susan Wise's zombie troops (including Hannah) killed him; interestingly, he took her place in Susan's army following the regeneration.

After regenerating, Hannah is rather confused – although clearly having Daniel's memories (she wakes up in his clothes), she also retains her own.

Much later, following Death Is But A Whisper, she becomes the Doctor again briefly until she hears the sound of glass breaking. Returning to the place she laid her father to rest, she discovers that he has regenerated...

Alternate Third Doctor ("M")
"M", the leader of the M.B.A. Squad and caretaker of Nanami, shape-shifts (through a belt-like device) in Azu-Who into the canon Third Doctor – stated to be done so he could fight the Master "with honor". The machine breaks later on, leaving "M" in that form until after Susan is defeated.

Alternate Sixteenth Doctor (Chiyo Mihama)
During Azu-Who, the interlocking dreams (complete with Daniel's voice narrating at points) of Daniel and his girls in Episode 6 show each watching themselves die; Daniel, throughout the last three dreams, noticeably breaks down and wishes to exact revenge on Davros (since the Cybermen and Sontarans were given their dues).

Daniel, as he dies in his own dream, entrusts the girls with fixing his TARDIS and leaving for the Universe to defeat evil. As they do so, Chiyo takes on the mantle and also becomes narrator (although she narrates from the point Daniel is shot by Davros, it is not revealed as her until near the end), writing a bit in the Doctor's diary prior to their first stop.

In Episode 24, a scene is shown of Chiyo meeting the First Doctor in the Rose Garden. As it ends, Osaka opens the door to the garden and calls out for "Doctor-Chiyo-chan", paralleling her usage of "Doctor-Daniel-sensei" to refer to Daniel himself.

Dr. Ishihara (Peter Cushing)
Dr. Ishihara, a character seen briefly in Azumanga Daioh, is alluded in Azu-Who to be the Doctor portrayed by Peter Cushing in two 1960s Dalek films that were shown in theaters. A later scene, where the First Doctor shows Daniel a dome in the Rose Garden which contains shrubs of the Time Lord's incarnations and companions from other universes, confirmed this.

Notably, Ishihara knows that Mayaa is an Iriomote cat but does not call Chiyo, Hannah, and Sakaki out on it. Like the Cushing Doctor, Suzie is related to him – here, however, she is his daughter.

(The author says the concept of Dr. Ishihara being the Cushing Doctor is attributed to an illustration from the Azumanga Daioh manga – one that made Ishihara bear a heavy resemblance to Cushing as he was in the 1960s.)

Canon Eleventh Doctor (Matt Smith)
In The Path of the Doctor, Hannah is shocked to discover that her father is essentially dead. The Doctor quickly explains to her the circumstances, putting things into order so things can pick up at The Eleventh Hour as canon dictates. Hannah tries to fight back, only to be sent back home with her memories suppressed...

Other Appearances
Unless otherwise noted, the appearances are of the First Doctor.

The Second Story
In this Altiverse, the Doctor returned to using his Seventh body (Sylvester McCoy) for his Thirteenth. Strangely, he dies from a bump to the head, falling off the TARDIS.

Beating 1,000,000-to-1 odds, he regenerates into a Fourteenth persona played by Allura McCoy. However, in an amusing twist foreshadowing that of Azu-Who fourteen years later, she has her own memories and must rescue her "predecessor" from a prison.

It is after this that the two begin a relationship, hence where Allura's last name comes from.

Azumanga Randomness (RPG)
The Doctor finally escapes from his "anomaly" status in the TARDIS through non-Daniel poster confusion, and later helps Akane and Susie heal; his relationship with Hannah is very similar to that of his own granddaughter Susan, which he eventually realizes.

While not seen in the revamp, he speaks with Daniel and Hannah through telepathy. It is revealed that the Doctor saw Ikuto close up the giant hole outside the school, and on a lighter note enjoys Ramen.

It Was Upon A Space Christmas
The Doctor (called the "Old Doctor") has an attitude similar to that seen from the 1963 Pilot through Episode 2 of Marco Polo in 1964. This may be due to suppressed emotions, as Rebekah and Sarah had died prior to this point.

Master Slave
The Doctor "purchases" Rachel from her uncle, a rich man who uses women as slaves, in April 2009. After this "purchase", he tells her that she is now free.

In 2034, the pair elect to stay behind on Earth while Daniel and Hannah return to the stars.

The Death of a MaCockenshipiel
The Fourth Doctor (Tom Baker) gives Chrissie MaCockenshipiel a bag of Jelly Babies and telling her not to let Death keep her from her journey. While she is unable to thank him face-to-face, her mother notices a few moments later that Chrissie has a floppy hat on her head.

The Dreamer Wakes
The Doctor and Rachel appear briefly, eating at a Ramen shop in 2034. "The Doctor saw it coming, but knew there was nothing he could do..."

His Thirteenth incarnation briefly appears in his post-mortem fate, suffering a double heart attack.