When sequels are made, whether they be of movies, video games, or books, the creators often add tidbits that acknowledge events, characters, or ideas that were present in previous works.
For example, in Call of Duty: Black Ops 3, there was a piece of dialogue that referenced Raul Menendez, the main antagonist of the previous Black Ops game. In Outlast 2, there were documents scattered throughout the game that referenced the infamous Murkoff Corporation from the first game. The same goes for The Last Of Us Part II.
This is a warning that there will be spoilers for both The Last Of Us games.
10 Guitar Lessons
At the very start of the game, Joel is playing the guitar for Ellie. He then hands the instrument to Ellie and says that he promised that he would teach her. This is in reference to the beginning of the level immediately following the escape of the cannibals in the first game.
Walking on the highway, Joel says that he will teach Ellie to play guitar when they finish up their business with the Fireflies and return to his brother's settlement in Jackson, Wyoming.
9 For The Love Of Coffee
In Pittsburgh of The Last Of Us, Joel and Ellie enter a dilapidated hotel. Upon entering the lobby, they come across a broken coffee maker. Joel expresses his love for coffee and how much he misses drinking it.
In The Last Of Us Part II, Dina and Ellie discuss Joel's infatuation with the caffeinated beverage when they enter a coffee shop on their first day in Seattle. There is another reference to Joel's love of coffee at the end of the game where he talks about trading for some coffee with newcomers to Jackson.
8 First Kill
In The Last Of Us, Joel is fighting with a hunter when he gets pinned under a puddle of water. He is unable to reach his pistol and it seems Joel is going to die when Ellie grabs it and shoots the hunter.
In The Last Of Us Part II, Ellie tells Dina this story when they arrive at the outskirts of Seattle on their first day. This story is Ellie's first human kill and prompts Dina to share the story of her first time.
7 Rabbit Hunting
In the first The Last Of Us, Ellie is seen hunting and killing a rabbit in the wintertime. This is the first time in the entire game where players take control of Ellie because of Joel's incapacitation from the previous section.
In The Last Of Us Part II, Ellie is on the outskirts of a farm when she is finishing up a hunt. The prey she brings back with her is none other than a rabbit, a reference to the rabbit that Ellie killed in the first game.
6 High Five
There is one instance in The Last Of Us where Joel and Ellie can high-five each other after crossing over the waterfall leading up to Tommy's Dam. Even though the high fives may seem like a small detail and insignificant, they do add to the character bonding between Joel and Ellie throughout the game.
In The Last Of Us Part II, Ellie has the opportunity to high-five someone again: Jesse. On her second day in Seattle, after fighting through a couple of stalkers and clickers, Jesse will raise his hand for a high-five to which the player (and Ellie) can reciprocate.
5 Bill's Town
Bill is a side character in The Last Of Us who is known for being extremely paranoid and isolated. He has the whole town of Lincoln, Massachusetts to himself, meaning no living humans reside there, just infected.
To protect from the infected, Bill has laid explosives traps and tripwires all over the town. Ellie comes across similarly made tripwires and explosives on her first day in Seattle in The Last Of Us Part II. The first interaction with these traps reminds Ellie of Bill, and she proceeds to tell Dina about Bill and his town.
4 Pallet Rides
Throughout the first game, Ellie is unable to swim, therefore, the player must use wooden pallets to move Ellie across flooded areas of the game. In the second game, Ellie has since learned to swim and no longer needs the pallets to travel across the water.
In a flashback, Ellie and Joel are swimming when they come across a couple of wooden pallets. Ellie makes a joke asking Joel for a ride, and Joel responds by saying that those days are far behind them now.
3 The Turning
In the DLC titled The Last Of Us: Left Behind, Ellie and her friend Riley sneak out of the Boston Quarantine Zone to explore a shopping mall. In the mall, there is an arcade where Ellie and Riley pretend to play some of the games. One of the games they play is called The Turning.
In The Last Of Us Part II, there is also an arcade that Ellie will come across on her third day in Seattle. After a bloater boss fight, the player can explore the area and find a bunch of arcade cabinets, a couple of which are the aforementioned game that Ellie and Riley once played.
2 Joel's Torture Method
The Last Of Us series is known for its dark themes in the games' storytelling. In the first game, Ellie is kidnapped and Joel has to find her. He captures two people who are with the groups that took Ellie.
Joel tortures them by forcing one of the two captives to write down where Ellie is being held, and the other confirms it. While in Seattle, Ellie and Dina come across two people who were victims of this very torture method. Players find out that Joel's brother, Tommy, performed the torture in this instance, but nevertheless, the method is the same.
1 No Pun Intended
Ellie has a joke book that she frequently refers to in the first The Last Of Us. She would randomly pull it out and tell jokes from it to Joel and other characters. While seemingly annoying to Joel, it still stuck with him.
During the guitar lessons interaction between Joel and Ellie at the beginning of The Last Of Us Part II, the former tells the latter about a joke that Tommy told him while out on patrol. He said that the joke made him think of Ellie. Even though this reference may not be as obvious as others, it is still a clever nod to the first game.