Twilight Sparkle and Spike. We know they are best friends, to the point of family. How did that bond, one so trivial that we take it for granted, even in real life, come to be forged?
War. War never changes. Unless we're talking the space of a hundred years or so, rockets and guns probably outclass spears and arrows in some way. Hmm... I'll get back to you on this. Eventually.