Twilight Sparkle has accidently sent Rainbow Dash to the past and now Rainbow lacks the means to power the time machine that she came in enough to return to her own time. Fortunately, her friends are still there to help her find a way to return to the present, even if they aren't exactly the same friends that she left behind.

Obviously inspired by Back to the Future, but the plot of this story is only loosely based on that of the movie.