Butterfly of Doom/Playing With

Basic Trope: A seemingly insignificant change in the past causes disastrous results in the present.
 * Straight: Bob travels back in time and accidentally kills a butterfly. As he returns to the present he finds that it has become a grim Crapsack World where humans are barely surviving.
 * Exaggerated: As soon as Bob materializes in the past, he instantly disintegrates because his arrival has dislodged a tiny grain of sand that caused all life on Earth to be wiped out at some point in less distant past.
 * Downplayed: "Close Enough" Timeline
 * Justified: Every small thing plays a significant role in the natural course of events, so changing one of these things will change the course of events.
 * Inverted: Bob travels back in time and accidentally kills a butterfly. When he returns to the present, he finds it to be a beautiful Crystal Spires and Togas utopia, with technology centuries beyond what he knew.
 * Subverted: As Bob returns to the present, he is horrified at what he sees and then is shocked as he remembers a butterfly he had accidentally killed. However, it turns out that these images and feelings were simply hallucinations caused by side effects of time travel.
 * Double Subverted: ...But then it turns out that these "hallucinations" were actually signs of the Delayed Ripple Effect.
 * Parodied: Bob stepped on a butterfly in the past, which leads to butterflies taking over the world.
 * Zig Zagged: As above, but it turned out he had just landed in the butterfly exhibit of the zoo...and then the moths come in and escort him to his cage.
 * Averted: Bob travels back in time and accidentally kills a butterfly. When he returns to the present, nothing has changed.
 * Enforced: "Hey, we need a filler episode to pad out this season. Let's let Bob screw with time travel."
 * Lampshaded: "All I did was step on a butterfly. How did all this happen?"
 * Invoked: Bob wants to destroy the world, so goes back in time and kills every butterfly he sees.
 * Exploited: Alice, knowing that Bob is an absolute moron, tricks Bob into going back in time, causing a chain of events which leads to Alice ruling the world.
 * Defied: Bob takes great care not to disrupt anything while in the past, especially butterflies.
 * Discussed: "Be careful. One little change here can destroy the Earth in the future."
 * Conversed: "Bob just stepped on a butterfly. That can't be good."

Back to Butterfly of Doom. Be careful not to step on anyth-- NOOOOO!!!