This has happened with the following shows especially:
1] 'Star Trek'
4] 'The Twilight Zone'
6] and of course, 'Doctor Who'
'The Hitch-Hiker's Guide To The Galaxy', 'Supernatural', 'Lost', 'My Favorite Martian' and even 'The Wild, Wild West' could also be responsible for changes to the timeline.
In "The Impossible Astronaut", a woman named Joy (possibly a secretary) was killed by a Silent in a White House Bathroom. She was blowed up real good, leaving nothing but charred paper-like fragments and ashes. As far as I can tell, the Silence killed her merely as a demonstration and threat of its power to Amy Pond.
Now, Amy was an interloper in that time period. She wasn't supposed to be there in 1969. If the Doctor had not brought her back to that year, or at the very least, if Amy had not chosen that particular moment to go to the bathroom, Joy would have lived.
In an uninterrupted timeline which did play out in Toobworld, Joy would probably have lived a long full life, had Amy not stepped into the picture.
The classic example of such a disruption is that of the butterfly killed in the dinosaur age, which created a massive alteration to the future. Joy may have been a secretary, but her life had meaning, creating ripples through her contacts with others. With her removed, History could be drastically altered - a la Edith Keeler in the 'Star Trek' episode "City On The Edge Of Forever" or Captain John Christopher in "Tomorrow Is Yesterday".
And speaking of the Edith Keeler episode, a similar situation happened to a character in that same story. Known as The Rodent, he found a Starfleet phaser, activated it, and was disintegrated.
Realizing this plot point meant an additional alteration to the Toobworld timeline, the Powers That Be addressed the issue with the remastered version of the episode. This time, he did not die and was able to live out his life the way it was meant to be.
I'd like to think that if Joy had to die and thus change History, than it should count for something, that her sacrifice should not have been in vain. I came up with a scenario - and even within the 'Doctor Who' corner of the universe! - in which her death mattered.
I realize this is damn near fanfic, but it does resolve another major problem with the overall Toobworld timeline which cropped up earlier this year.
The 'Torchwood' - "Miracle Day" mini-series.
Let's say "Miracle Day" occurred in the original timeline (or at least the one after the Eleventh Doctor "rebooted" the whole universe.) Scientists working for "The Three Families" discovered an alien rock formation that ran the entire length of the Earth's core and which was responsible for ending death among humans. It was an intriguing idea in the short run, but the natural ramifications it spawned should have sent seismic shock waves across all the world - and thus throughout the entire TV schedule.
Just with the United States alone, martial law was invoked and "death" camps were set up. Sure, most of the TV shows being produced were on summer hiatus by that point, but why didn't we see signs of the new world order in shows like 'Burn Notice' in Miami, 'White Collar' in New York, and in the "Miracle Day" backyard - 'The Closer' in Los Angeles. Such drastic measures as those taken by the government in "Miracle Day" would not have been dismantled as quickly as they were set up, so we should have seen or heard about the event in the Fall TV line-up. A show like 'Person Of Interest' would have brought it up by now.
So 'Torchwood' - "Miracle Day" is probably the biggest Zonk ever to strike the Toobworld Dynamic.
With Joy's sacrifice, hopefully we can rectify that.
Joy appeared to be in early middle age. She may have been married - I didn't see a wedding ring in her brief scene - but that could just mean that she was divorced. It could be that she had children.
If so, perhaps one of them would grow up to be a geologist, whose scientific research while working for the Three Families' corporation could have led to the discovery of the Blessing.
Here's the TARDIS description of the Blessing:
The Blessing was the name given to a second pole of the Earth, going from Buenos Aires to Shanghai. The Three Families used it to cause the miracle, by feeding it the blood of immortal Captain Jack Harkness.
The Three Families discovered the Blessing's presence by realising that the average lifespan of people living in Shanghai over the Blessing was the exact same as the global average human lifespan, and had been so throughout history. The Blessing was the focus of a morphic field matrix that encompassed all humankind, and the Families were able to alter it by introducing Jack's blood on both sides of the fissure. Jack speculated that the Blessing perceived this as an attack, which is why it was trying to keep everyone alive. As a mortal, Jack's blood was attracted to the Blessing. Introducing his mortal blood on both sides, via Jack himself and Rex Matheson, reversed the process. It was later sealed off by UNIT.
Despite being in charge of the Blessing, the Families were unsure of its nature, such as whether or not it was a living organism. When pressed by Gwen, Jack speculated that the Blessing was something spoken of in a Silurian mythology he had heard of from the Doctor, and could have been caused by an interaction with the huon particles of the Racnoss hibernation field, but was forced to admit he had no idea.
In the new timeline caused by the death of Joy, the grief and shock over his missing Mom (Remember, she didn't leave behind a body to be found.) could have affected her child so deeply that maybe he - or she - changed their original plans for the future. Perhaps instead of becoming a scientist, a career in law enforcement, even the FBI, was the path taken.
Eventually the Blessing would be discovered, but it didn't have to be manipulated into causing "Miracle Day" if it was discovered by someone or some organization other than PhiCorp and the Three Families. It could be kept secret, so that it no longer affected other TV shows, and the upheaval in society would be minimal.
It also means all those TV characters who died during the course of the ten part miniseries would still be alive.
And all because Joy was murdered by the Silence back in 1969.
At least, that's one way to go.....