Another description for episode 17:
Jefferson, a young rakishly handsome, former criminal who in Fairy Tale Land has given up his life of crime and dedicated himself to his daughter, while in Storybrooke he is a dangerous and mysterious figure who has knowledge of the Evil Queen’s curse and attempts to persuade Emma that it is real.
Also. based on an interview with OUAT’s creators, I think the hat refers to the “Mad Hatter” from Alice in Wonderland. “'We find out how the Mad Hatter became mad,' Kitsis teases…So how will this Wonderland be different from what we already know? 'The first [difference] you'll notice is in who the Mad Hatter was and his backstory. Then what Wonderland is and [its] changes is something we hope to explore also,' Kitsis says. 'We're hoping this tells you the story of the Mad Hatter, but will also leave you questions about Wonderland.'”
http://uk.eonline.com/news/watch_with_kristin/once_upon_time_bosses_dish_on_mad_guest/296279#ixzz1nawrfCLr
Based on these two sources, I think that Jefferson from Stroybrooke is the Mad Hatter in FTL. Jefferson is considered “mad” in Storybrooke because he believes the fairy-tales in Henry's book are true and will tell Emma he thinks they're real.
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy