ontological paradox
can it be avoided? when going to change the past?
examples:
In the 2008 television miniseries The Andromeda Strain, the aforementioned disease is sent back in time via a wormhole by the citizens of future Earth, who cannot stop the disease because a required bacterium has gone extinct and only exists in the past. Scientists in the past manage to utilize this bacteria and kill the virus, but a single sample is saved and stored in the International Space Station at the series' end. It is implied that this sample is the cause of a viral outbreak on the future Earth, causing its citizens to once again send the virus back and hope that it can be destroyed in the past. This creates a further paradox due to the fact that the disease seems to have no origin and only exists in the past because it was sent from the future, whose citizens kept a sample from the past and then sent it back again, creating a never-ending loop.
In the Family Guy episode "Meet the Quagmires", Peter travels back in time to his senior year of high school. At the prom, Brian sings Rick Astley's hit 1987 single "Never Gonna Give You Up", creating an ontological paradox as it serves as Astley's actual inspiration for the tune.
On his 30th birthday, a man who wishes to build a time machine is visited by a future version of himself. This future self explains to him that he should not worry about designing the time machine, as he has done it in the future. The man receives the schematics from his future self and starts building the time machine. Time passes until he finally completes the time machine. He then uses it to travel back in time to his 30th birthday, where he gives the schematics to his past self, closing the loop. Of course, the schematics must have come from somewhere.