In Spite of a Nail/Playing With

Basic Trope: Despite changes in the past, improbable events still have occurred in the present.
 * Straight: Bob goes in back in time to kill Hitler before World War Two and succeeds. He still exists, despite his dad's parents having met in the war.
 * Exaggerated: Bob destroys the asteroid that killed off all the dinosaurs. Humanity still evolves.
 * Justified: There are mysterious forces that try to keep the timeline on track.
 * Alternatively, since Bob changed history, he still exists in order to prevent a paradox
 * When Bob travels to other universes, he ensures his machine can only send him to realities where he exists. Since there's an infinite number of worlds, he could find a version of himself where the Nazis won WWII.
 * Inverted: For Want of a Nail
 * Subverted: Bob is shocked when discovers he prevented his father from being born.
 * Double Subverted: It turns out that his father was born in a different part of the world.
 * Parodied: Bob causes many changes during his time travel trips, but no matter what, his parents will still meet and his favorite movies still exist.
 * Deconstructed: It turns out it has an effect later on.
 * Reconstructed: The world is much better and everyone is happy.
 * Zig Zagged: While the new present appears to be very different from the old one at first, there are still inexplicable similarities.
 * Averted: History changes in the way that one would expect it to happen.
 * Enforced: "We don't want to scare people into thinking that they might accidentally wipe themselves from existence."
 * Conservation of normality and detail are more important to the work's creators than realism, so they simply decide to rely on Willing Suspension of Disbelief for the sake of storytelling.
 * Lampshaded: "I can't help noticing how some things remain the same in this new timeline."
 * Invoked: Bob says that he knows that if he kills Hitler, his paternal grandparents will still meet.
 * Defied: Bob made sure to change every single thing he can think of to make sure the present he came back to will be completely different.
 * Discussed: "Time Travel does not work that way. If you managed change something in the past, there are bound to be some unexpected consequences!"
 * Conversed: "Why is it that whenever these characters succeed in changing something, there aren't any unexpected consequences?"

You know, even if you went back in time and made sure nails were never invented, you'd still be able to go to In Spite of a Nail.