Dodo Chaplet

Dorothea "Dodo" Chaplet was a companion of the Doctor near the end of his first incarnation. He took to her within seconds of their first encounter, citing her physical similarity to his granddaughter. (DW: "Bell of Doom") Indeed, she was perhaps most notable for being the first Human female to have travelled alone with the Doctor. (DW: The War Machines)

She had relatively limited contact with other companions, only having spent significant time with Steven Taylor. She briefly met Polly Wright in 1965's London — and was with her when she first encountered Ben Jackson. Still, the relationships were superficial, and neither the sailor or the secretary had even seen the TARDIS when Dodo decided to stop traveling with the Doctor.

Aside from those companions who were actually American — and discounting Martha Jones' walk across the globe that never happened — Dodo was likely the companion to have traveled most broadly in the United States. She visited Florida, New York City (PDA: Salvation) and Arizona. (DW: The Gunfighters) Indeed as a percentage of her total travels in the TARDIS, she almost certainly had the most visits to America. She was also one of the few companions known to have lost her virginity whilst an active TARDIS traveler. (MA: The Man in the Velvet Mask)

However, most details of Dodo's life — her childhood, the reasons she both started and stopped traveling with the Doctor, and even her death — were shrouded in a confusion created by several highly contradictory accounts.

Early life
Dodo's grandfather was French. (DW: "Bell of Doom") However, she didn't speak or understand French, largely because she skipped her French lessons in school in order to learn how to kiss behind the school gymnasium. She grew up in one of the poorest parts of London, but when her parents died, she moved in with an aunt who was financially more comfortable than her parents. Moreover, her aunt was a social climber, which afforded Dodo exposure to a wide variety of social experiences in her young life. She had difficulty believing that the squalid existence into which she'd been born, and the world to which her aunt aspired, were part of the same reality. As a coping mechanism, she continually reinvented herself depending upon the situation in which she found herself, claiming to have "acted all [her] life". Thus, her accent was sometimes Cockney and at other times posher. (MA: The Man in the Velvet Mask) Her relationship with her aunt may not have been particularly close, as she believed that she wouldn't be missed when she left her home to travel in the TARDIS. (DW: "Bell of Doom")

Another view of her youth
According to an alternate account of her youth, Dodo's parents did not both die when she was young. Rather, Dodo's mother had died in an accident, an event that the Celestial Toymaker would later, cruelly, have her re-live. Her father suffered a mental breakdown and had to be hospitalized. Dodo was sent to live with her great-aunt, Margaret. Her great-aunt forced her to spend time helping an elderly neighbour do his shopping and other menial tasks. One night, an alien ship crashed nearby and its pilot killed the neighbour, assuming his physical form. When Dodo learned what happened to her friend, the alien kept her prisoner for some time, until she was able to escape. When she did escape, she rushed across Wimbledon Common, heading straight for what she thought was a police box. (PDA: Salvation)

Meeeting the Doctor
As a young adult in the 1960s, Dodo witnessed a small boy getting hurt. Seeking help, Dodo spotted a police box on the common and entered it. Instead of a policeman, she found the TARDIS. Like Tegan Jovanka and her Aunt Vanessa, Dodo thus became one of only a few people to ever attempt to use the TARDIS as an actual police box. Instead of getting help for the boy, she was immediately spirited away to the distant future with the first Doctor and Steven Taylor. (DW: "Bell of Doom")

Travels
The Doctor took his companions to New York City in the same time period, where they met and defeated the alien's compatriots. (PDA: Salvation)

Dodo's youthful vigour and excitement in all she saw reminded the Doctor of Susan, and the pair became close. She took the TARDIS, and Space/Time Travel, in her stride. The fact that the TARDIS wasn't a police box made her intrigued, rather than incredulous. When Dodo experienced Time Travel, she was equally excited about being on the Ark (DW: The Ark) as she was later to be in the Wild West. (DW: The Gunfighters)

When Dodo, and the travellers, arrived on the Ark she, at first, believed that they were at Whipsnade Zoo. Dodo told the others that she went there as a child, and she displayed some knowledge of nature. Unfortunately, Dodo had a cold, and this virus was accidentally passed on to the Humans and Monoids inhabiting the Ark. As they had no resistance to this virus it became a plague. Dodo, being a caring person, was distraught that she had caused this terrible event. (DW: The Ark)

Dodo's caring nature was probably what made her dislike cheating, unfair, behaviour. Whilst this annoyance could be seen at many times, it was most visible when the travellers met the Celestial Toymaker. It was his games, attitude, and Cyril's cheating which frustrated Dodo. (DW: The Celestial Toymaker) Whilst travelling with the Doctor, Dodo was lucky enough to have one of her life-long wishes granted. She was keenly interested in the Wild West, and revealed that she had always wanted to meet Wyatt Earp. When the travellers arrived in the American West, the Doctor introduced Dodo as "Miss Dodo Dupont, Wizard of the ivory keys". During their time in this era the Doctor noted that Dodo was "fast becoming a prey to every cliché-ridden convention in the American West." (DW: The Gunfighters) Despite this, and the sad events on the Ark, Dodo's interest, and excitement, were still evident as the travellers continued on their journey. Dodo was not frightened to investigate on her own, and on the next planet they visited she wandered off while the Doctor and Steven were busy with the Elders and the Savages. She had a look around this planet, and discovered the laboratory of Senta, which was used for the life-force transferance that kept the Elders alive. (DW: The Savages)

This independence may finally have been Dodo's undoing. When the travellers returned to 1966 London and discovered WOTAN and its War Machines, it was Dodo who WOTAN conditioned to betray the Doctor. On discovering this, the Doctor broke her conditioning, and sent Dodo to the country to recuperate. Dodo never returned, instead she sent her TARDIS key back with Polly, saying that she had decided to stay in London. (DW: The War Machines)

Life after the Doctor
Dodo would suffer severe and recurrent psychiatric problems as a side effect of being controlled by WOTAN. Shuttled from hospital to hospital, she was eventually sent to the Glasshouse, where she was brutally interrogated by its director, the Master, about the Doctor. Turned out into the street, the homeless Dodo eventually met and fell in love with journalist James Stevens, at that time investigating the activities of UNIT. While Stevens was being interviewed on a live television broadcast, Dodo was murdered by Francis Cleary, a former UNIT soldier, Glasshouse patient, and another of the Master's hypnotically controlled pawns.

The Doctor, in his second or seventh incarnation appeared at the funeral and attempted to give solace to Stevens. (MA: Who Killed Kennedy)

Another account shows Dodo to be alive and well in the 1990s (BE: Ships)

Will the real Dodo Chaplet please stand up?
As on television, where she only had about four-and-a-half stories, Dodo is one of the least-featured companions in other media. Unfortunately, most all of these other appearances conflict with each other. The Man in the Velvet Mask opposes Salvation over what Dodo's childhood was like. Salvation differs with Bell of Doom over why she initially approached the TARDIS in Wimbledon Common. Mask, Who Killed Kennedy and Ships all disagree over what might have killed her in the 1960s or 1970s — or even whether she died at all in those decades. To be sure, other companions do have stories which differ over the odd biographical detail. For example, we can wonder, thanks to SJA: Death of the Doctor, whether Liz Shaw actually died. (NA: Eternity Weeps)  However, the degree of difference between individual Dodo stories is unusually high — approaching that of Ace, who effectively has several alternate timelines.