Picard: Change them? You mean change the past? Q, even if you have been able to bring me back in time somehow, surely you must realize that any alteration in this timeline will have a profound impact on the future.
Q: Please! Spare me your egotistical musings on your pivotal role in history. Nothing you do here will cause the Federation to collapse or galaxies to explode. To be blunt, you're not that important.
— Star Trek: The Next Generation, "Tapestry"
"Seriously, little wren, suppose my father-in-law, that abominable King Victor, had died in youth, as he nearly did. Suppose my mother-in-law, Queen Mary, had married Georgie York, who was secretly very fond of her—only he could not show it, being so English. Why, then you would have had a quite different Royal Family from the one you have now. But do you suppose anything else would have been the smallest bit different? Pooh!"
— King and Joker, Peter Dickinson
Harvey: All modern research points to the elasticity of time, rather than a brittle framework.
Crichton: Can it be corrected?
Harvey: If nudged closely enough to course, events have a way of restructuring themselves. If the participants are the same, the venue's the same, the motivation's the same, then, well, the outcome is likely to be the same.
— Farscape, "Different Destinations"
Giga: Interesting..... What's different?
Rock: Well, Bass is a robot like me, and we generally get into fights. He was made by Doctor Wily, a mad scientist I usually fight, but I will sometimes do other activities with him, like Soccer. I don't know what else is different, though I do sometimes hear Doctor Light be disappointed that his internet advancement research didn't go anywhere.
Giga: Dr. Wily is my enemy as well....He wants revenge on the world because his robotics research wasn't funded.
Rock: ...Wow. So, Dr. Wily doesn't get it right either way...