Starlight was practicing a new spell when she accidentally ends up transporting a group of Napoleonic soldiers to Equestria. Shenanigans ensue.

Also, did I mention there was a zombie plague?

Twilight Sparkle assigns Starlight Glimmer the task of 'Mapping out the castle'. Starlight thinks that this is a ludicrous idea, I mean, who needs a map for a building?

As it turns out, Starlight Glimmer did.