When history has changed, and the protagonists must fix it, but there's no reason for it to have changed, that's a Wayback Trip. Unlike Set Right What Once Went Wrong, where the time travelers go back and defeat the villain, and as a result, history is changed for the better, in this trope, the time travelers go back and defeat the villain, and as a result history stays the same. The ultimate result is then either a Stable Time Loop (Rome always had secret lycanthropires all along) or a Close-Enough Timeline, perhaps in which the protagonists Tricked Out Time (there were no monsters the "first time around", and the second time, there were but no one will be the wiser).
This trope seems to derive from the Adventure Towns treatment of Time Travel. Periods of history are treated like places rather than points on a timeline. New York in 1897 isn't the cause of New York in 2007, it's just 110 years earlier, and is free to have its own history and events.
This could technically be considered a case of Make Wrong What Once Went Right and Terminator Twosome, in that the protagonists are changing history to make their (that is, our) timeline happen instead of the one with Roman vampire werewolf sorcerers.
- In one episode of Wandaba Style, the girls accidentally travel to the past, when Teen Genius Susumu was a mere Child Prodigy. While there, they encourage him to follow his dreams, and even act as guinea pigs for toned down versions of experiments he'll run in the future, yet when they return to the present, nothing at all has changed.
- This trope is the basic premise of the Terminator movies (even though side effects cause some ontological paradoxes).
- Doctor Who does this all the time, especially in the new series.
- In the original series serial "Pyramids of Mars", Sarah Jane asks why they have to stop the villain destroying the Earth in 1915, when they know it's fine in 1980. In reply, the Doctor takes her to 1980 . . . and it turns out to be a desolate wasteland. Apparently, once the Doctor arrives somewhere, he must complete the Stable Time Loop to maintain the "proper" version of history. (In which case, one wonders — and this question has been voiced in the series — why the heck does the Doctor keep travelling around?! Arguably, if he didn't, the effect would be that 1980 Earth had always been a desolate wasteland, and there wouldn't be a "real" 1980 for Sarah to come from).
- It's pointed out by Martha in "The Shakespeare Code". The Doctor explains that it is similar to Back to the Future. Except this doesn't make sense either; in BttF, Marty was the one who altered history, whereas in the episode, the witches existed totally independent of the Doctor's travels. The general Hand Wave is that things have gotten really screwy since the Time Lords died off.
- In "Blink", the Doctor explains that time, rather than being a linear chain of cause and effect, is actually "a big ball of wibbly-wobbly, timey-wimey stuff." This apparently explains everything.
- The new series has also introduced the idea of "fixed points", which amounts to there being some things you can change, and some things you can't. Even though several villainous plots would have averted those fixed points if they had come to fruition — Omnicidal Maniac plans to destroy the universe / the multiverse / reality itself have shown to have succeeded because the Doctor had been killed in a For Want of a Nail scenario, but this still did not cause the Time Crash messing with a fixed point does even though said-points hadn't even happened yet. At least once, a fixed point in time was actually engineered. The rules for them aren't exactly set in stone either.
- The TV series Quantum Leap. In one episode, Sam leaps into various points of Lee Harvey Oswald's life. As it turns out, in the "real" history, Jackie Kennedy was killed too.
- Every episode of Voyagers! The series did mention "the flow of history being tampered with", implying that the changes were caused by other time travellers.
- In Chrono Trigger, if you visit the pre-historic time period, and then beat the game without causing the humans to defeat the Reptites, will give you an ending where the Reptites became the dominant species on the planet. However, beating the game before landing in that time period, that future doesn't come to pass, implying that simply landing in the past causes the Reptites to win. In fact, the "World of Reptites" ending isn't caused by the landing in the past, but by the fact that to beat Lavos at this moment, you'll have to take Ayla with you; and, since she's the most skilled human fighter and the only one who would attack the Reptite headquarters... Also, it is implied that the Gate Key incident may have motivated the Reptites to attack Laruba village and get very serious. If Crono and co. never arrived in 65 million BC, that never would have happened.
- The main plotline of Mario & Luigi: Partners in Time. Aliens invade the past Mushroom Kingdom, causing mass destruction and taking over the castle... but the only effect this has on the present Mushroom Kingdom is the time portals that suddenly appear in the otherwise-intact castle. Technically, the time holes appeared due to an unrelated event that was nonetheless destined to happen so that the bros could travel back in time in the first place. Specifically, from timey machine go boom.
- In the various Caverns Of Time instances in World of Warcraft, the players' goal is preserving some event in Azeroth's history the way it should be, by defeating The Infinite.
- Sluggy Freelance:
- "The Stormbreaker Saga" involves Zoe and Torg going back to medieval times and stopping the demon K'Z'K (who they blasted into the past in an earlier arc) from conquering the world. How this works in terms of a Stable Time Loop or Delayed Ripple Effect is made more confusing by this strip, which thankfully invokes Bellisario's Maxim to lampshade it.
- Zoe also claims that the answers to her history test changed over night, with the new answers being in line with her experience in the past. The internal consistent theory of time travel is not revealed to the readers. (If there is one.)
- The trope name comes from Peabody's Improbable History, a segment on Rocky and Bullwinkle. In every episode, Peabody and Sherman would visit a historical personage with some problem that kept them from doing what they were supposed to do historically, and help them with it. In the first appearance of this segment, it is explained that a straight-up Time Machine is actually rather boring since not everyone in the past is famous. So, Mr. Peabody invented a "Should-Have-Been" machine to ensure that his trips will be interesting rather than historically accurate.
- Used and lampshaded in The New Mr. Peabody & Sherman Show, where the duo travel to the past in order to have stories to share on their late night talk show. For the season finale, everyone Peabody and Sherman had helped petition to get the show cancelled, blaming Peabody for causing more overall harm than good with his time traveling.
- Time Squad is often thought of as a throw back to Peabody and Sherman; with a time cop and a prissy robot and an orphaned kid to guide them. They go around time traveling and fixing people because in their universe, in the future, time has gotten so old and worn-out that they have to fix glitches constantly.