I predict that the secret episode will be like the final episode in bbs.
I also predict that the character wont be terra, aqua, or ven, rather i think it would be either eraqus or xehanort.
Or even better, the secret episode is gameplay between bbs and kingdom hearts 1.
Playing as xehanort in radiant garden and learning of the experiments with the heartless and nobody would be so cool haha
