Kyon: Hey, Nagato. Could you make it rain on the day of the game? A huge one that'll cancel the game.
Nagato: It is possible. However, it is not recommended.
Kyon: Why's that?
Nagato: Alterations to the local environmental data may result in aftereffects on this planet's ecosystem.
Kyon: How long before these aftereffects show up?
Nagato: Between a few centuries and ten millennia.
Kyon: Then I guess we probably shouldn't.
—The Boredom of SuzumiyaHaruhi
Setsuna shook her head. "Some past events are crucial, but the time stream can absorb many minor changes with no major effects. Butterfly effects are rare. Plus, Himeko needs to learn how to judge the likely consequences of actions." She turned to Himeko. "With practice, you'll become good at telling if some action is likely to have wide-ranging consequences or minor ones. This is a good way to learn."
— Sailor Moon Z, Episode 19
"It's called the Butterfly Effect. You step on a Butterfly, and a year later three million people end up dead."
— Angela Petrelli, Heroes
Martha: But are we safe? I mean, can we move around and stuff?
The Doctor: Of course we can. Why not?
Martha: It's like in those films: if you step on a butterfly, you change the future of the human race.
The Doctor: Then don't step on any butterflies. What have the butterflies ever done to you?
— Doctor Who, "The Shakespeare Code"
Erica: What about paradoxes, huh? Butterfly Effect, Back to the Future?
Dr. Tom: I love that movie.
Erica: If I change the past, if I don't get drunk, would that cause, like, World War III in the present?
Dr. Tom: Or, is it possible that your alcohol consumption, though very important to you, might not play a role in influencing world events?
Cassie: Why can't you second-guess history? I mean, if you could go back and change things so that the U.S. was ready to fight earlier [in World War II]...
Ms. Paloma: Because events are intertwined in ways we cannot always see, Cassie. Sometimes small things can make huge differences. You know, they say that a single butterfly, beating its wings in China, may affect the way the wind blows here in our country. A single butterfly beating its wings may make a tiny change that becomes a bigger change that becomes a tornado. The world isn't like math. It isn't just one plus one equals two. It's more complicated than that.
Rachel: [thinking to herself after class] But how is the butterfly supposed to know when to beat her wings?
— Animorphs, book 7, page 134
Jake: [after the Animorphs have destroyed the Kandrona generator, Jake yells to the Ellimist] Is it enough? Is it enough? Have we changed the future? [no response]
Rachel: I don't think he knows. He showed us a possible future. But you know what? I don't believe the Ellimist really knows the future any more than we do.
Jake: What makes you so sure?
Rachel: [laughs] Because wherever it is that the Ellimist exists, and whatever he's up to, and whatever game he's playing, and no matter how mighty he is, he has butterflies, too.
The Ellimist: [laughing with a voice that comes from nowhere] HA, HA, HA, HA. AS I SAID, YOU ARE A PRIMITIVE RACE, AND YET YOU ARE CAPABLE OF LEARNING.
— Animorphs, book 7, page 161
Sometimes we're on a collision course, and we just don't know it. Whether it's by accident or by design, there's not a thing we can do about it. A woman in Paris was on her way to go shopping, but she had forgotten her coat, went back to get it. When she had gotten her coat, the phone had rung, so she'd stopped to answer it, talked for a couple of minutes. While the woman was on the phone, Daisy was rehearsing for a performance at the Paris Opera House. And while she was rehearsing, the woman, off the phone now, had gone outside to get a taxi. Now a taxi driver had dropped off a fare earlier and had stopped to get a cup of coffee. And all the while, Daisy was rehearsing. And this cab driver, who dropped off the earlier fare; who'd stopped to get the cup of coffee, had picked up the lady who was going to shopping, and had missed getting an earlier cab. The taxi had to stop for a man crossing the street, who had left for work five minutes later than he normally did, because he forgot to set off his alarm. While that man, late for work, was crossing the street, Daisy had finished rehearsing, and was taking a shower. And while Daisy was showering, the taxi was waiting outside a boutique for the woman to pick up a package, which hadn't been wrapped yet, because the girl who was supposed to wrap it had broken up with her boyfriend the night before, and forgot. When the package was wrapped, the woman, who was back in the cab, was blocked by a delivery truck, all the while Daisy was getting dressed. The delivery truck pulled away and the taxi was able to move, while Daisy, the last to be dressed, waited for one of her friends, who had broken a shoelace. While the taxi was stopped, waiting for a traffic light, Daisy and her friend came out the back of the theater. And if only one thing had happened differently. If that shoelace hadn't broken, or that delivery truck had moved moments earlier, or that package had been wrapped and ready because the girl hadn't broken up with her boyfriend, or that man had set his alarm and got up five minutes earlier, or that taxi driver hadn't stopped for a cup of coffee, or that woman had remembered her coat, and got into an earlier cab, Daisy and her friend would've crossed the street, and the taxi would've driven by. But life being what it is - a series of intersecting lives and incidents, out of anyone's control - that taxi did not go by, and that driver was momentarily distracted, and that taxi hit Daisy, and her leg was crushed.
—Benjamin Button: The Curious Case of Benjamin Button
"Don't do anything that affects anything, unless it turns out you were supposed to, in which case, for the love of God, don't not do it!"
—Professor Farnsworth, Futurama ("Roswell That Ends Well")
"So, despite the temptation, altering the timeline is more foolish than productive. Anybody who would built a space-time object replacement device is a complete moron."
—Professor Membrane, Invader Zim ("Big Bad Rubber Piggy")
Return to the Butterfly of Doom here, but DON'T... TOUCH... ANYTHING!