During the BW pre-release I remember Cheren appearing in an early screenshot. We thought he was a female gym leader, turns out he was a rival.

Bianca popped up too apparently but I don't remember anyone mentioning her.

N's "Pokemon are friends" shot popped up weeks before his official announcement. I remember everyone cooing over the hot new rival.

So..Anyone taking bets over what shown NPCs are going to be important?

I'm still betting the girl with brown hair is the rival and not a random trainer who just appears to be following X.