Humanity's space exploration ultimately took the form of billions of identical probes, capable of building anything (including astronauts themselves) upon arrival at their destinations. One lands in Equestria. Things go downhill from there.
Crossover between XCOM: Enemy Unknown and MLP. Twilight appears on Earth, shortly after the alien war. How will she cope with being taken prisoner? How will XCOM cope with the single most powerful psion they've ever encountered?