So, we have:
1) RH but problems of maid marian and whether connected to Tamara
2) Eric, in a version of little mermaid where Regina takes the Ursula /Vanessa role
3)Hook but not new, complicated history with two villains, plus already connections with Neal and Emma to explore
4)Triton/male merman, in a flip of the little mermaid story. They did say he would “surface”.
5)Tinkerbell or Ariel but Regina’s past love/interests male. Of course they did hint Regina might not reciprocate the attention.
6)Some character not cast yet appearing in the past in SB, Land without magic, or FTL or NL, or present in NL.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass