For some, I think it would be quite interesting to have some sort of extraterrestrial quality to MLP. Of course not to alter completely the future plot. For example, what if an extraterrestrial space craft crash landed on Equestria and the alien of the crash wasn't familiar with friendship because it never has had contact with their world? The Mane-6 could teach friendship to this being and then when the extraterrestrial leaves their world, it could then teach the rest of its civilisation what it learned while on Equestria.