Fourth Doctor/Other realities
Various versions of the Fourth Doctor existed in other realities. These counterparts shared similarities to the Fourth Doctor of his universe, despite existing in parallel universes or alternate timelines.
Other realities
Aborted timelines
When the Faction Paradox altered events to cause the Third Doctor to regenerate on Dust, (PROSE: Interference - Book Two [+]Loading...["Interference - Book Two (novel)"]) the Fourth Doctor went on to combat the Eight Legs, (PROSE: The Blue Angel [+]Loading...["The Blue Angel (novel)"]) but was only able to halt their eventual conquest of the universe. (PROSE: The Ancestor Cell [+]Loading...["The Ancestor Cell (novel)"])
In a timeline created by the War Master's usage of the Anti-Genesis codes, the Fourth Doctor, Sarah and Harry were ambushed by the Master's Daleks upon arrival on Skaro, exterminating them. (AUDIO: Shockwave [+]Loading...["Shockwave (TWM audio story)"])
Under the influence of the Valeyard and the Dark Matrix, the Fourth Doctor was corrupted into destroying the Daleks at their very beginning. This timeline was negated when the Seventh Doctor defeated the Valeyard and released the Dark Matrix from his control. (PROSE: Matrix [+]Loading...["Matrix (novel)"])
In the Warrior's universe, the Doctor was persuaded by Sarah Jane to complete his mission to avert the Daleks' creation by destroying the incubation chamber. He, Sarah and Harry went to retrieve the time ring but were confronted by a surviving prototype Dalek which exterminated his companions and mortally wounded the Doctor. The Doctor was extracted by Narvin who informed him his actions had led to a Time War and the Daleks still existed. Narvin supplied the Doctor with an elixir so he could regenerate, with the Doctor choosing to become a warrior to face the Time War. (AUDIO: Dust Devil [+]Loading...["Dust Devil (audio story)"])
In an alternate timeline created by the Discordia, the Doctor had a passionate romantic relationship with River Song that began in his first incarnation, having married her by his fourth incarnation. When he learned that the only way to defeat the Discordia was to dismantle his timeline, the Doctor admitted that he was afraid to lose River, but was reassured that they would meet again in another timeline. (AUDIO: Someone I Once Knew [+]Loading...["Someone I Once Knew (audio story)"])
In a negated timeline, the Doctor and Leela met the Eighth Doctor's companion, Charley Pollard, when she appeared aboard the TARDIS. As he had detected temporal disturbances in the Time Vortex, the Fourth Doctor realised that Charley was one of his companions from the future. He then met the Eighth Doctor himself and they both discovered the Decayed Master was plotting their undoing by removing their TARDIS from history. After Charley and Leela vanished, the Doctors were caught in the explosion of the Fifth Doctor's TARDIS, but were saved by the Sixth Doctor. Once a plan to stop the Master was conceived, the Fourth Doctor went to keep the Master distracted with the Eighth Doctor, and, once the Fifth Doctor had ensured that the TARDIS would not explode, joined his other seven incarnations in preparing to time ram the Master's TARDIS. However, rather than kill the Master, the First Doctor instead turned off the automatic distress actions, which had brought all of the Doctors to the pocket dimension and triggered the TARDIS' destruction, making it so none of that had happened. (AUDIO: The Light at the End [+]Loading...["The Light at the End (audio story)"])
At two different points in the Doctor's fourth incarnation, one during his time travelling with Leela and another during his adventures with Romana's second incarnation, the TARDIS picked up the signal of a temporal distorsion coming from the planet Henlen, and the Doctor went to investigate. With the Doctor and Leela in a thick jungle and the Doctor and Romana in an ever-changing city, the Doctors and their companions were pursued into a refuge where they found writings in ancient Gallifreyan, and realised they were in the TARDIS prototype that was used for the first experiment of time travel by the Time Lords, and that they were being chased by the original six pilots, who explained that the experiment was sabotaged by the Sirens of Time.
They turned into the starting point of a massive temporal paradox, which was splitting reality apart, and which trapped the pilots into a time loop. They begged the Doctor to stop the experiment and kill them, but he refused. The leader then chose to have the experiment fail himself, thus causing Time Lords never to discover time travel. As a result of his choice, the Doctors, Romana and the TARDISes were erased from time, and Leela was left to die at the hands of the Sirens. However, these events were later cancelled when the paradox was resolved. (AUDIO: Collision Course [+]Loading...["Collision Course (audio story)"])
When the Cybermen allied with Rassilon to take over history, (COMIC: Supremacy of the Cybermen [+]Loading...["Supremacy of the Cybermen (comic story)"]) the Doctor was confronted by a cyber-converted K9 while facing the Cybermen in a mansion, (COMIC: Prologue: The Fourth Doctor [+]Loading...["Prologue: The Fourth Doctor (comic story)"]) and was then ambushed by the Cybermen. This timeline was eventually unwritten by Rassilon and the Twelfth Doctor. (COMIC: Supremacy of the Cybermen [+]Loading...["Supremacy of the Cybermen (comic story)"])
While travelling in E-Space, the Doctor arrived on the planet Veridis, where scientists had created a machine that could bring the dead back to life, this discovery completely destabilising society as everyone clamoured for their loved ones to be brought back from the dead. The Doctor was able to destroy the machine, but this was only possible when he and Romana sacrificed themselves to destroy it. Adric was left to make a life for himself on Veridis as the TARDIS decayed and K9 ran out of power, but when he began to experience dreams of the destruction of N-Space in the Doctor's absence, Adric developed his own time machine to go back and undo the events of the Doctor's death so that he could live to save the universe again. (AUDIO: A Full Life [+]Loading...["A Full Life (audio story)"])
Parallel universes
In a parallel universe where the Valeyard defeated the Sixth Doctor in the Matrix, the Valeyard went on to try to stop his fourth self's trip to Logopolis in order to prevent its destruction and benefit from the resources. When he tried to stop him, he accidentally time-rammed his younger self's TARDIS, along with the Master's TARDIS, destroying them both. (AUDIO: He Jests at Scars... [+]Loading...["He Jests at Scars... (audio story)"])
