Doctor Who: The Newbies Guide
This is the eighth story in Season 3.
Where does this fit?
This happens very shortly after The Celestial Toymaker.
The first Doctor looks like a human in his sixties. He is physically quite frail, but has a keen intellect. He is paternalistic towards his companions, and has a degree of arrogance towards others. He sometimes mispronounces words. He acquired a toothache at the end of The Celestial Toymaker
Steven Taylor was a space pilot from an unknown time in the future. His spacecraft landed on the planet Mechanus, where a group of robots called Mechanoids held him prisoner. In The Chase, he escaped when the Doctor, Ian, Barbara, and Vicki visited the planet whilst on the run from a Dalek time machine. He stowed away on the TARDIS not knowing it was capable of time travel.
Dorothea Chaplet (commonly referred to as Dodo is a girl from 1966 England who (in The Massacre) ran into the TARDIS on Wimbledon Common, thinking it was a genuine police box.
Recurring and Historical Characters
A number of the guest characters are real people.
The Earp Family were lawmen who took part in the gunfight at the OK Corral. Virgil was the oldest, and in real life the senior lawman at the gunfight. In most fictional accounts, Wyatt is portrayed as the leader and senior lawman. Warren is their younger brother.
Bat Masterson was another famous lawman. In real life, he was not present during the gunfight.
Doc Holliday was a dentist who fought beside the lawmen at the gunfight.
The Clanton Family. Pa Clanton was a cattle rancher. Most of his sons (including the notorious Ike) were part of a loose group of outlaws by the name of the Cowboys, who were involved in cattle rustling. Many of them were fighting against the lawmen at the gunfight.
Johnny Ringo was a member of the outlaw group known as the Cowboys. He fought against the lawmen at the gunfight.
This story draws quite heavily on the Western genre. If you're not at all familiar with it, you might want to see a Western movie or two.
You might want to read up on the historical gunfight at the OK Corral, though the version here isn't entirely historically accurate.