* Subverted in ''Film/StarTrek2009''. Although Kirk's father is killed when the U.S.S. ''Kelvin'' is destroyed by temporally-displaced Romulans, the 23rd century was more or less the same as in ''Series/StarTrekTheOriginalSeries'' (aside from getting a [[CosmeticallyAdvancedPrequel cosmetic facelift]]). That is, until [[spoiler:Vulcan gets destroyed, too]]. WordOfGod said that [[spoiler:Vulcan was destroyed]] specifically to show that [[NothingIsTheSameAnymore anything goes in this new timeline]].
** Happens in the 30th anniversary episode of ''Franchise/StarTrek'', "Trials and Tribble-ations", which revisits the events of the [[Series/StarTrekTheOriginalSeries original series]] episode "The Trouble With Tribbles". Though they manage to foil Arne Darvin's plot to kill Kirk with a bomb disguised as a tribble, their very presence in the past causes a minor change in the timeline, as seen when Kirk is looking for who started the fight with the Klingons; said scene is edited to include Chief O'Brien and Doctor Bashir.
** Another episode had Sisko attempting to invoke this: Sisko, Bashir, and Dax are sent back to Earth's [[CrapsackWorld Crapsack Past]], and the guy who's supposed to trigger the events that make things better winds up getting killed preventing some thugs from mugging them. Sisko is well-versed in history enough to take the guy's place, assuming his name and doing the things the dead man [[TimeTravelTenseTrouble was supposed to going to have done]]. This results in a timeline that's pretty much the same as the one they left... except Starfleet has some questions for Sisko about why he suddenly always looked exactly like historical hero Gabriel Bell.
* Discussed in the ''Series/StarTrekVoyager'' two-parter "Year of Hell", where a Krenim scientist named Annorax created a weapon capable of [[RetGone erasing his people's enemies from history]], but ForWantOfANail ensured this often also did things like eliminating the sources of cures for plagues, ultimately hurting the Krenim. He's been trying to fix it all with more and more erasures for the past 200 years, and finally manages a 98% restoration of the Krenim as they were before he started. His subordinate asks if this is a CloseEnoughTimeline, but Annorax has become a KnightTemplar and insists it isn't. Somewhat understandably, this is because the 98% restoration still doesn't include Annorax's lost wife, who was wiped out with the very first erasure attempt. In the end, it turns out that the only way to fix everything is to erase the weapon itself, [[NoOntologicalInertia thus undoing all of the changes it ever made]].
** Subverted in ''Film/StarTrek2009''. Although Kirk's father is killed when the USS ''Kelvin'' is destroyed by temporally-displaced Romulans, the 23rd century was more or less the same as in ''Series/StarTrekTheOriginalSeries''. That is, until [[spoiler:Vulcan gets destroyed, too]]. WordOfGod said that [[spoiler:Vulcan was destroyed]] specifically to show that [[NothingIsTheSameAnymore anything goes in this new timeline]].
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