Ronnie is a short-tempered Boston quarantine zone resident Joel passes near a checkpoint in The Quarantine Zone. If you stop to listen, he is gossiping about his friend Mark, and he snaps at Joel for staring.
Linger near the pair and Ronnie calls Joel an asshole. His friend tells him to shut up, assures Joel they want no trouble, and Joel lets it go. The friend then asks Ronnie if he knows who that was, and Ronnie shrugs it off.
The conversation is optional, but it gives you a picture of life under FEDRA: weeks of half rations, beatings, and people who disappear into lockup.
He stands near the checkpoint Joel and Tess cross in 20 Years Later, the opening stretch of the chapter. Not long after, a Firefly bomb wrecks a military vehicle there and soldiers clear the street. His friend's question about whether Ronnie knows who Joel is hints at how few people in the zone want to cross Joel and Tess.
Mark
Mark is a Boston quarantine zone resident who is only talked about. In The Quarantine Zone, Joel can overhear Ronnie telling a friend that soldiers caught Mark using fake ration cards.
Ellie Williams
Ellie Williams is the 14-year-old girl Joel is hired to smuggle out of Boston, and your companion for most of The Last of Us Part I. She was bitten weeks earlier and never turned, so the Fireflies believe her immunity could lead to a vaccine. You play as her in the winter chapter and in the Left Behind DLC.
Joel Miller
Joel Miller is the man you play for almost all of The Last of Us Part I. A hardened smuggler in the Boston quarantine zone, he takes a job escorting 14-year-old Ellie out of the city, and the drop-off turns into a year-long trip across the country to find the Fireflies.
Malick
Malick is a tough in the Boston slums who tries to block Joel's path in The Quarantine Zone. Tess knows him and sends him back to his seat with a single word.