MLP/Warhammer 40K crossover. Chaos Space Marines from the piratical 38th Company have engaged Tau forces around a planet rich with alien life, magic, and... friendship? I guess? Weird.
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.
Devoid of memories and found in the Everfree Forest, little Raichu is nursed back to health by Twilight and her friends. Little do they know about the importance of her past and how far she’ll go to repay their kindness.
An accident with the Mirror Portal ends up with Twilight stuck as a small pony in the Equestra Girls' world. Her friends can't get over how cute she is.