Fallout: Nuka Break/WMG

The passerby whose hat falls off in Eastwood is The Courier

Since it's become fairly obvious, or at least largely accepted, that the town of Eastwood is actually the Divide before its destruction, it's not exactly a stretch to assume that the man in the duster that Twig bumps into is actually the Courier, maybe on his first run through the Divide, that sets off the events of Lonesome Road, and Ulysses' Start of Darkness.

• Jossed, for now. Zack Frinfrock has stated on his twitter the whole Eastwood = Divide thing is wrong and a complete coincidence since they had never planned for Eastwood to go that route. Since the set of Eastwood was destroyed, they have to re-write season 2 anyways (again, through Frinfrock's twitter) it's entirely possible that at some point he'll go "fine! Whatever, we'll go with that!" But Jossed for now regardless.
  • Well, it probably still could be. In Lonesome Road its mentioned that most of the Courier's work before the events of New Vegas was mostly in the NCR, and considering the name of the Courier's version of Ulysses' duster, the Courier Duster (not possessive, as in, the Courier's Duster), it could be a general issue thing all couriers get. And said "hatfalloffguy" had a coat very similar to it.
• In Episode 6, he is revealed to be the Mysterious Stranger.

The NCR Veteran Ranger is a descendant of Ben

Since the info he provides seems to be Ben's full name, and the ring is how he says he knows who Ben is, it's more than likely he shares something personal with Ben's family from before the bombs dropped. Given how long ago that was, it's either a debt somebody owed Ben, or Ben fathered a kid before everything went to hell, and now a descendant is looking out for his forefather.