>>131811in most of the good stories there are usually 2 variations:
1) a time travel version (usually relatively close in time difference) example is a pretty good comic called "Tomorrow's me" or something like that where the girl travels a day or two in the past
2) Some kind of alternate reality version. example of this is one of my favorites from xxxenophile called Doppelgangbang i think. In this comic the two main characters encounter alternate reality versions of themselves that are gender swapped
