Board Thread:General Discussion/@comment-31512959-20161223050356/@comment-25375217-20161223060344

I agree that it likely has the ability to cross realms. I like your theory that he somehow harnessed mermaid magic, I didn't really have an explanation for it.

If it can cross realms, that would also explain why Nemo doesn't seem to fit in with the Enchanted Forest, and possibly how Liam was able to age - they were in another realm where time was able to pass. Say, what if they ended up in the Dark Realm...? That could explain why Nemo is coming back.

Unfortunately, the show didn't make it clear. Like you said, it couldn't have come in on that dirigible, but Nemo may have, and then Liam and some of the rest of the crew were left behind but came to Storybrooke on their own. That's the likely, but non-canon, explanation.