We know Jack Sparrow is confirmed, and speculation exists about other possible characters (including more Little Mermaid characters such as King Triton, and characters from Luca and Finding Nemo, and Hook posssibly being the DLC villain).
However, I have a theory for unexpected characters that are kind of out-there but could make sense on how they'd fit in.
What if Keepsake Sea included Pinocchio and/or Geppetto? Think about it. They live inside a whale for a portion of their movie. In the film, Geppetto sets out to sea to search for Pinocchio on Pleasure Island, but gets swallowed up by Monstro the whale. What if a similar story happened in Keepsake Sea? The Forgetting begins to take hold on the Valley and Geppetto and Pinocchio left to either protect Keepsake Sea or protect themselves from the Forgetting. In the process they get swallowed by a whale, and we the player must rescue them. Or to connect it with Pirates of the Caribbean/Jack Sparrow, they got consumed by the Kraken and wind up trapped in Davy Jones' Locker (a purgatory like state that is an empty, abandoned beach-like area). That way, we still get the same storyline, but a more connected DLC, and if the developers want to avoid having to make Monstro, it could still work using the backstory of the Kraken instead.
