Corporal "Dickhead" is the nickname Ellie and Riley give a FEDRA officer at the Boston military boarding school. He is only talked about in Left Behind, as the man who took their water guns away.
In Fun and Games, Riley surprises Ellie by pulling the confiscated water guns out of her bag, having taken them back from the corporal at real risk. The two use them for a water fight, and Riley gives Ellie both guns afterward because she is leaving with the Fireflies.
In Mallrats, a water gun poster in Liberty Gardens sets Ellie off: she tells Riley she already tried to sneak the guns out of the corporal's office and got caught on the way out. Riley tells her to forget it, and Ellie swears she will still get them back. That makes Riley's surprise later in the night land harder.
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.
Riley Abel
Riley Abel is Ellie's best friend from the military school in the Boston quarantine zone and the co-star of the Left Behind DLC. She appears in the Liberty Gardens flashback chapters Mallrats, Fun and Games and Escape from Liberty Gardens, and Ellie brings her up during the main story.
Winston Asher
Sergeant Winston Asher is a FEDRA soldier who once kept a camp and a horse in Boston's Liberty Gardens mall. In Left Behind, Ellie and Riley find his empty camp in Mallrats, and his notes show how he saw the two girls.
Anna
Anna is Ellie's mother, known only through a letter Ellie carries and a few remarks from people who knew her. You can read her letter, the Note from mom artifact, from Ellie's backpack at the start of Lakeside Resort.