In 1989, "Doctor Who" was canceled, which meant that a number of ideas for the future of the show were scrapped. The most interesting of these ideas was the story of the Other.

Back during the classic series, the Time Lords were a regular part of the series. The Doctor was exiled from Gallifrey, so he wasn’t there most of the time, but there were recurring Time Lord characters, such as the Master. The writers felt as though the Doctor was “boring” due to the fact that he was just another regular Time Lord, as well as the fact that a lot of the more mysterious parts of his backstory had already been told. Therefore, they came up with a story to make him mysterious again.

There are three Time Lords who “founded” Time Lord Society. Rassilon, who watches of the modern series will recognize from the Tenth Doctor’s final episode, "The End of Time," as well as the recent finale of Series 9, "Hell Bent." The second founder was a Time Lord named Omega, who hasn’t appeared since the tenth anniversary episode, "The Three Doctors." The third was named The Other, and we haven’t seen him at all.

Below: Rassilon from "The End of Time"

Omega harnessed power from a supernova to enable the Gallifreyans to time travel. This act made him go down in history as a hero, as he apparently died in the act. He really survived and made it to an anti-matter Universe, where he went mad and had to be stopped by the Doctor. Rassilon took control of Gallifrey, and ruled it with an iron fist.

Here, our sources differ. See, the Time Lords had “looms” that could “weave” children out of genetic material. Either they became sterile for some reason, or the “looms” were a sign of status. It’s likely the latter, because they were, in some way, related to Rassilon’s dictatorship. The Other made sure his granddaughter, Susan, was safe, and then he threw himself into the Looms as an act of defiance.

The Other’s genetic material was then reconstituted into the Doctor. From there, the story is fairly straightforward. The Doctor stole a TARIDS and ran away. He used one of Rassilon’s things to travel backwards into Gallifrey’s timeline-which is against the rules-and picked up Susan. Susan recognized the Doctor as her grandfather. The two agree that they aren’t really related, but it just seems right that they are. Susan became the Doctor’s first companion, and boom. Rassilon was killed at some point, and later revived for his appearance in the modern series.

This story is most likely not canon with the revived series. In "Name of the Doctor," we see Clara’s various selves splintered across the Doctor’s timeline. One of these selves directs Susan and the First Doctor into the TARDIS. This contradicts the idea of the Doctor picking up Susan in Gallifrey’s past. There are pieces of this story that are in novels and such, and there are a few hints dropped towards the end of the classic series, but for the most part, this remains just a fun story from the 80s.