Well, we had a new character introduced in the very end scene of the final episode of Season 3, and guess who it is?
Actually, it's not difficult to guess at all, so might as tell you (stop reading now if you don't want to know).
It's Elsa from "Frozen" emerging from a bottle and showing off her powers. No word yet on who will play her next season (or anyone else, for that matter).
We'll be back next year to cover all the new episodes of "Once Upon a Time," Season 4.