Reset Button

We can easily fix blowing the whole Earth up by simply pressing our friendly neighborhood Reset Button!

The Reset Button is a trick employed in any form of media that undoes any recent events the main characters experienced so that said events never really occurred, effectively making them Non-Canon in some cases. Episodic TV shows are partially immune to past events being considered Non-Canon as every following episode acts like a Reset Button (unless there is a Two Parter). A Reset Button can be totally avoided by having an Experience Souvenir make an appearance, alluding to the past events and showing that they were in fact real.

There are some UnTrashes that can be considered Reset Buttons. All Just A Dream is a terribly infamous example of such an UnTrash. In it, the dreamer is shown going through a realistic series of events that likely leads to a fatal end. However, just before they die, they wake up and notice that their experiences weren't real, resetting to the time before they fell asleep. Another form of a Reset Button is a Factory Reset where, at the end of the story, characters (likely main ones) simply forget certain details of recent occurences.