In the Disney film, when Jiminy opens the book to tell the story of Pinocchio, there are two other books visible on the shelf.
One is Peter Pan and the other is Alice in Wonderland.
So, there’s is a connection between the 3 stories – Pinocchio, Peter Pan, Alice in Wonderland.
We know August knows Neal/Bae and, if suspicions are correct, Peter Pan.
We know there is some connection between Neal/Bea and Alice in Wonderland – we have the Cleaner’s and Hatter’s sign and the monacles in his apartment and there’s an Alice In Wonderland statue in Central Park.
So, I believe Neal/Bae knows Jefferson. I believe they met in Neverland at some point before the curse. Being that Bae (PP) was probably jumping between our world and Neverland for centuries, at this point, he already had his our world alias (Neal Cassady) and told Jefferson what his name was. Jefferson knows everything about Bae and probably Rumple and what happened between them – could be part of the falling out Rumple and Jefferson had and partly why Jefferson stopped his ‘work’ with Rumple (along with whatever happened to Grace’s mother).
So, let’s just say – Pinocchio knows Peter Pan, The Mad Hatter knows Peter Pan and I think The Mad Hatter and Pinocchio know each other, also.
I think August made at least one other trip to Storybrooke, prior to when we see him arrive in True North.
I think it was before he ran into Neal/Bae.
During that trip, August meets up with Jefferson. Jefferson tells him about Neal/Bae. August goes in search of him and finds Emma.
When August returns to Storybrooke, 10 yrs later, he reconnects with Jefferson. Jefferson tells him about the book, because Jefferson wrote it (which is another theory, entirely).
They work together, August adds his story – at Jefferson’s house – he’s clearly not at his room at Granny’s when he does this.
Jefferson is the one that tells August about the dagger.
Jefferson is the one August is talking to on the phone when he says they have to excelerate the plan.
August and Jefferson are the only 2 ppl in SB that are shown actively trying to convince Emma to believe.
There are also deleted scenes showing August at Jefferson’s house.