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 caterpillar seed that caused all life on Earth to be wiped out at some point in less distant past.
- Bob travels 30 years in the past and moves a chair. When he gets back, he finds that somehow, there are now dinosaurs working for the FBI.
- 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.
- Bob is in a Stable Time Loop, and couldn't change things even if he wanted to.
- Enforced:
- "Hey, we need a filler episode to pad out this season. Let's let Bob screw with time travel."
- "We can't just let Bob change the entire status quo with time travel. Something bad must happen to force Bob to undo everything."
- 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 a moron, tricks Bob into going back in time, causing a chain of events which inexplicably leads to Alice ruling the world.
- Defied:
- Bob takes great care not to disrupt anything while in the past, especially butterflies.
- Rather than immediately head back to the present, Bob meticulously examines the timeline for any events resulting from his changes that pave the way to the Bad Future, and irons them out to ensure the intended future without any negative consequences plaguing it.
- 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."
- Deconstructed: The people in the new timeline don't have a say in whether they want the timeline to be fixed. Fixing the timeline won't save them; it will finish them off. When one of the people he encounters points this out to Bob, he now has a Sadistic Choice on his conscience: leave the people in his original timeline in oblivion, or send the people he created there instead?
Back to Butterfly of Doom. Be careful not to step on anyth— NOOOOO!!!
