It's the news all of us Oncers, Once Upon a Time fans, have been waiting for! Michael Raymond-James had been confirmed to be reprising his role as Neal/Baelfire! For those of us who have been missing him since season 3, this will definitely be a treat! There were some precautions taken to keep this hidden, including flying in incognito, staying with friends, and doing his scenes away from paparazzi.
Even with all the precautions that were taken to keep his part in Season 5B under wraps, it was found out that he did indeed do some indoor filming. These are the three possible reasons his character, Neal/Baelfire, could be back and in the Underworld.
Neal has only truly loved one woman and that was Emma. Their relationship was just starting to rekindle when Emma and Henry had to leave Storybrooke due to another evil curse. Emma's first love was Neal and they had a child together. Before he died, there was still hope for these two to finally have a happily ever after. Maybe that hope and love is his unfinished business and is keeping him in the Netherworld.
When Neal finds out he is a father he is angered and hurt that Emma kept this from him. Once he does find out, he puts his whole heart into it. Neal would visit Henry, took him to eat, watched over him, and told him stories. Not to mention risking his life to try to save him. He missed out on so much unknowingly, so I'm sure he would not want to miss another moment. This could definitely be a valid reason for him being trapped there as well.
His one wish was for his father to be good and normal again. That was his whole reason for even coming to this world in the first place! Rumple was not safe or anything close to it when Neal died. It is quite possible that his father's unknown safety and happiness could be what is holding him back from moving 'on' from the Underworld.
No matter the reason this is a reason to rejoice! Baelfire is back in action and the next half of Season 5 is right around the corner! March 6th needs to hurry up and get here already!