In the previous game, Joel mentions wanting to teach Ellie how to play guitar at some point once their adventure was over. Looks like that happened.
Look at the windows in the room Ellie's sitting in (best visible when Joel walks in). It looks like the same windows from the opening menu of the first game.
Not only are the lyrics to "Through the Valley" that Ellie sings in the trailer a good indication of her Then Let Me Be Evil mindset, the rest of the lyrics that we don't hear are a pretty good match to the original story of the game too, both in regards to Ellie and Joel's famous ending decision:
Well I came upon a man at the top of a hill
call himself the saviour of the human race
Said he come to save the world from destruction and pain
But I said how can you save the world from itself
It could also be referring to how the cult will play a role in this game. Seeing as how they cult refer to Ellie as a wolf, and they probably see themselves as the shepherds saving the "sheep" or call themselves "saviors of the human race".
Joel's death also leads some fridge to one of the lines Ellie sings as the camera focuses on him or his ghost/Ellie's imagination:"... and I will dwell on this Earth forever more."
Some have noted that the people in the cult look incredibly similar to each other. Now you can chalk it up to Naughty Dog using the same skins to save time when creating characters, but remember these people are in a cult. Of course they're going to look the same.
Just like the first game, Part II revolves on a mission the protagonists are out to fulfill that they end up not doing in the end; "create a vaccine from Ellie", and "kill Abby". However, just like the first game's story isn't actually about "create a cure from Ellie", but the growing bond between her and Joel and Joel finding meaning again in his life, Part 2 likewise isn't mainly about "killing Abby", but Ellie coming to grips with Joel's death and learning to forgive both him for lying to her and herself for shutting him out of her life, and realizing that killing Abby does not pertain to this.
The "Rat King" might seem like an odd name for the horrific creature you meet, unless you look it up. Rat Kings are a real (if rare) phenomena, where several rats end up conjoined by the tail, usually due to their swarming nature, it isn't even a death sentence, some specimens have been noted to have their tails beginning to callus, which indicates long term joining, it's actually a perfect name for it.
Looking at a map of southern California, it might be confusing as to why the Fireflies were apparently setting off from Santa Barbara to Catalina Island instead of the much closer and more numerous Channel Islands. However, since the latter have no real infrastructure compared to the former, they wouldn't be as fitting of a place to do the type of work that needed doing. Of course, that raises its own Fridge Logic as to why the Fireflies didn't just set off from Long Beach, assuming they're even still around.
The prevalence of rhyming storylines. Ellie and Abby are playing out different parts of the same story: the emotional toll of a Roaring Rampage of Revenge. Abby's story also rhymes with Joel's from the first game: a cold, broken, traumatised survivor finds a measure of healing and redemption by protecting and caring for a young person. Owen's arc even gets a rhyme in the Apocalyptic Log of the Firefly that Ellie and Joel find at the Wyoming Museum: a one-time true believer of the cause who became disillusioned after one too many acts of violence and oppression.
Ellie's tattoo features a moth, and so does her guitar. Abby used to be a member of the fireflies. Ellie is chasing after Abby. Moths are known for being drawn to light. The loading screens are of moths fluttering toward a light.
It makes sense that Ellie and Dina would find gasoline in a synagogue. It would not be the first time there was an oil based miracle in a Temple.
In Abby's story, Lev is worried about an attack and Yara replies "She protects us". It is not the Prophet that Yara references as protecting them anymore; she means Abby will literally protect them.
One of the first shots of the teaser shows a tree with deep claw marks in it. Given how none of the first game's infected had claws this indicates that we'll likely have new types of infected able to leave a mark like that. Or it could even be an infected animal.
Which, in retrospect, could bring back on the table what was originally in store for the first game: Like this infected LION...◊
Pretty much the only reason the first game did not have a Downer Ending (just a very bitter Bitter Sweet Ending) was that, basically, Ellie lived and showed herself to be a decent person in spite of everything. The second game's teaser - just the teaser!! - shoots that all to hell by revealing Ellie has become just as cold, bitter, angry, unstable and violent as Joel regretted becoming. Retroactively, the first game is now Ellie's Start of Darkness!
Even worse is how the last game ended. Ellie believes that there are others immune to the cordyceps infection like her. It could be possible that during the Time Skip or later in the game she learns the truth and how Joel basically lied to her about the Fireflies. If they're the focus of Ellie's Roaring Rampage of Revenge, it could pretty much mean that it's All for Nothing!
Although Ellie's targets are indeed former Fireflies, she's not after the group as a whole, so this one is essentially Jossed. All for Nothing still summarizes the plot pretty well, though, with all that implies.
When the WLF launch an all-out assault on the Seraphites main base near the end of the game, their leader Isaac commits every able-bodied fighter to the attack. Everyone. Then the assault fails, leaving a homicidal cult as the only somewhat combat-ready faction in greater Seattle. It's not hard to imagine that the survivors will want payback, and with the WLF home base now mostly unprotected, another massacre is already brewing on the horizon, especially since the Seraphite island is a burned-out ruin while the WLF base is still intact. Keep in mind there are children at both bases, and neither side has any qualms about killing kids.
The main theme of the game is the Cycle of Revenge. Both Abby and Ellie kill hundreds of people in an attempt to get revenge on each other. Anyone of those victims could have friends and family that are now thinking the same thing. Going after both Abby, Ellie, and their loved ones ensuring the Vicious Cycle never ends.
The moment Ellie learns the truth from Joel. It’s not just that he basically lied to her. It’s that he effectively destroyed humanity’s best, and only chance at stopping the Plague by killing the leader, senior officials, and surgeon.
Assuming Bill is still alive, how would he react to finding out that not only Tess was dead the entire time (something he didn't know about in the previous game) but that Joel has now died as well? As if losing Frank wasn't enough...
Jesse's parents are mentioned in Ellie's journal. Imagine what their reaction was like when they found out about his death. Granted, a letter presumably from Jesse's mom that can be read at the farmhouse states that she doesn't blame her for his death… which itself is Fridge Horror and Dramatic Irony because Ellie actually unknowingly left her map behind at the aquarium after killing Owen and Mel, and this then led to Abby and Lev finding them- so it really WAS (indirectly) her fault in a sense.
Since Ellie dropped the map that noted her hideout after killing Owen and Mel due to the shock that the latter was pregnant, does she ever find out that she was indirectly responsible for the events at the theatre that lead to Jesse's death and herself, Tommy and Dina almost dying? If so, imagine the guilt she must've felt on top of losing Joel...
During their final confrontation, Abby bites two of Ellie's fingers, but if you look closely, she only bites off Ellie's ring finger. That almost certainly means that Ellie had to amputate her pinky by herself later.
When Ellie and Dina find Eugene's porn tapes, Dina pronounces the title of Smash Brandi's Cootch with the same syllable emphasis as the name of what it's parodying, Crash Bandicoot. However, since Dina is roughly the same age as Ellie and thus was born well after the outbreak, it's unlikely she would have heard of the game to begin with, and therefore wouldn't have pronounced the title how she did.
Well, in "Left Behind" Riley quoted the 1939 Wizard of Oz movie (as in, you know, Ruby Slippers) and electricity exist in the more post-post apocalyptic zones (”Kids will be watching movies Tonight!") so it is not like media and culture was swallowed by a black hole during Outbreak Day, never to been seen or talked about again. And people in this world REALLY enjoyed their PS3s and Naughty Dog titles.
Adding onto this, taking into account this game's infamous "Vita girl" who spends both of her scenes devotedly playing Hotline Miami, it isn't very farfetched to guess that Ellie and/or Dina got the chance to play Crash Bandicoot at some point in their lives, especially in the large, cozy settlement of Jackson that's as close to the old world as the post-apocalypse can get.
The long-abandoned basement of the WLF hospital in Seattle contains a bunch of live infected including the unique Rat King. All of them are trapped alone in locked isolation chambers when you first arrive, implying they're some of the first infected from the original outbreak 25 years ago and have been there ever since. This raises some questions, like why are there only Stalkers and Clickers around (infected this old should've evolved into Bloaters long ago), and how are they even still alive after more than two decades without food? After all, infected are Technically Living Zombies that are repeatedly shown to be requiring nourishment, which makes the entire thing come across as the devs plonking down some enemies for the sake of enemies, logic be damned.
It's possible that the lack of anything for nourishment is exactly why there are Stalkers and Clickers, they can't grow the necessary mass required to become Bloaters or "fruit" they might be sustaining themselves with their own fungal infection and what little food they can find.
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