A lightning bolt to Celestia's horn, aside scaring a brony crapless on his own dimension, also warps him to a random plain on Equestria. After being rescued by Twilight Sparkle who watched the whole thing, he's brought to a hospital and now is keen on making sure not to fall on any of these crazy situations that always come up when someone decides a human appears in Equestria. And he can do it. After all, who would be best suited to avoid being dragged into weird situations than a fanfic reader?

Aside that person you just thought of. And the next dozen, too. (I'm not experienced with stories, but I promise I'm trying to make a good one for the first real try.)