During my recent reread I was thinking about this thread and I had a whole bunch of stuff I wanted to mention. Of course, I forgot most of it. Anyway...
Mentions of Marwyn are peppered throught the books, probably 5 or 6 times. Y-Storm pointed out Mirri Muz Dur mentioning him in this thread. Qyburn mentions him, his book is brought up and I forget the other times he's mentioned. Given that he's headed Mereen, maybe he's to play a significant role.
Arya has been destined to go to Braavos-she's missed several opportunities to be recognized (both a good and bad thing) and something always stops her from reaching any planned destination. Headed to wall-Yoren's killed. None of the northmen at Harrenhal recognize her and she doesn't tell Roose Bolton who she is- this probably saves her life. Escapes Harenhall right before Jaime gets there (he probably would have recognized her or Brienne may have made the connection). Ends up at inn where Jaime and Brienne had recently been. Talks to the old lady prophet on the same bridge where Robb and Catelyn stop to have a chat, most likely less than a day of two after Arya's departure. Had they run into each other Arya would be having a bad time time at the Twins with them. Also, if the outlaws would not have seen the maegi, they would would have not known of the Wedding and would have walked Arya into Gregor's seige at Riverrun. Sandor and Arya show up at the twins just late enough to avoid walking into the massacre. They head to the Vale, which is the new home of her sister. The Hound can't continue so off she goes to Saltpans, where she gets cheated for her horse, can't pay the ship for passage and desperately produces J'aqen's coin.
Useless trivia:Arya unknowingly calls her would-be husband stupid. Elmar Frey, Bolton's squire who is afraid of leeches, ducks out of leech duty mumbling about something he forgot and Arya says "I forgot, you're stupid." Later he is angry because he lost his chance to marry a princess. She could care less about some spoiled princess, which is actually her-she was part of Catelyn's deal with the Freys.
The girl who offers to ring Gendry's bell is his half-sister.
"Maggy the Frog" seems to be Lady Sybell's mother.