UNIT/Other realities
Versions of UNIT existed in various alternative realities relative to the usually-recorded Doctor's universe.
Parallel worlds
The fascist Britain in the Inferno universe had its own version of UNIT, the Republican Security Forces, led by a counterpart of Lethbridge-Stewart. (TV: Inferno)
The Seventh Doctor visited one parallel universe in which humans had made peace with the Silurians after the Wenley Moor affair. In this universe, United Races Intelligence Command or URIC had replaced UNIT. An alternative version of Muriel Frost headed the organisation, following the death of the Brigadier in a bomb attack; this world's Doctor was killed in the same attack. (COMIC: Final Genesis)
In the Unbound Universe, Alistair Lethbridge-Stewart became the Brigadier of UNIT but had to face alien attacks without the Doctor's assistance. These included the “Plastic Purges”, lizards (which required the sacrifice of Mike Yates via time travel to stop) and the Ambassadors, who left a string of crators along North America. The Brigadier took drastic actions against these attacks, including bombing Surrey. (AUDIO: Sympathy for the Devil) In 1972, UNIT encountered the Daleks. Three Daleks were able to kill 47 men. (AUDIO: Masters of War) Due to UNIT's many disastrous failures, Alistair was regarded as a dangerous crackpot and ultimately driven out from UNIT. In 1997, he and the Doctor encountered UNIT forces in Hong Kong led by Colonel Brimmicombe-Wood. (AUDIO: Sympathy for the Devil)
In one parallel universe, a version of the Doctor was associated with UNIT, exploiting his credentials with the organisation to gain the confidence of Professor Eric Vollmer. (AUDIO: Full Fathom Five)
In Pete's World, President Harriet Jones created UNIT by merging Torchwood and the Preachers. UNIT was headquartered in Big Ben and the Meta-Crisis clone of the Tenth Doctor served as its scientific advisor. (AUDIO: The Siege of Big Ben)
Aborted timelines
During the Year That Never Was, the Saxon Master's agents used technology previously belonging to UNIT, among other secret organisations. (AUDIO: Deceived)
Other
In the unstable mini-universe created by the Monk, (PROSE: No Future) the Wenley Moor incident resulted in the Silurians conquering Earth, with the remnants of UNIT led by Lethbridge-Stewart fighting a vicious insurgency against them. (PROSE: Blood Heat)
A deliberately altered timeline saw UNIT fighting a counter-insurgency against a British anarchist terrorist group named Black Star. A plain-clothes division named Broadsword had been created. (PROSE: No Future)
In a parallel world, UNIT soldiers retrieved the dead body of the Tenth Doctor following the Christmas Star incident, and later a division of UNIT worked with Rose Tyler to reverse-engineer the TARDIS and allow Donna Noble to go back in time and make her younger self turn left instead of right at a junction. (TV: Turn Left)
