WARNING: The following contains spoilers for Season 4 of Attack on Titan, now streaming on Crunchyroll, Funimation, Hulu and Amazon Prime.
The final season of Attack on Titan has been busy filling in many of the gaps that the story has created over the years. This makes the foreshadowing in some of the earlier seasons extremely rewarding. Looking more closely at the past, there's even a big clue to the reveal of Marley and the outside world all the way back in Season 2. At the time, the clue definitely seemed like some sort of hint, but to what fans could only speculate. Now, with all the new information that has been pouring out from Season 4, it is clear that this hint was far more revealing than we ever realized.
In Season 2, Episode 4 "Soldier," we get the first major clue that there is a world outside of the island and, potentially, people who know about it. The revelation comes when one of the Scout squads takes refuge at Utgard Castle for the night while they look for the breach in Wall Rose. Among the senior members of the Scouts, there is also Reiner, Ymir, Bertholdt, Connie and Christa (before she reclaimed the name Historia). Looking back, it's almost nostalgic seeing them all together again, especially given the current set of circumstances in Season 4.
They start to rummage through the castle's old supplies for things to eat or drink. Ymir, taking a moment by herself to search for food, is stumbled upon by Reiner. As they talk, Ymir pulls out a can of herring -- a seemingly innocuous item. But the fact that she can read the writing on the can gives her away to Reiner. Reiner instantly recognizes that the canned item cannot be from the island, especially given that the label is in a language that only Ymir can read.
It's just when Reiner is starting to put two and two together that they are interrupted by an attack on the castle. But for those of us rewatching the anime, this is a huge moment of foreshadowing. It clues us in to the fact that foreign languages and foreign people exist in the series, something that, at the episode's time of airing, was totally unknown and unthought of. The fact that Reiner seems to know more than he lets on makes it even more of a pivotal moment.
Though it was unclear at the time, Reiner must have pieced together then that Ymir isn't from inside the walls. In the process, Reiner's own backstory comes to light. After all, without his own outside knowledge from Marley, he wouldn't have been able to understand how and why Ymir is able to read the can -- or the significance of it. Plus, he also recognizes that canned food isn't something that people should have within the walls. He knows what canned food is, he's just surprised to see it there.
While this moment seemed vaguely mysterious at the time, the knowledge we have now makes it downright explosive. Perhaps more in-depth rewatching will reward even more moments of intense foreshadowing. With the final season of Attack on Titan winding down, it's easy to look back with even greater fondness on the early seasons. Hopefully when the series is wrapped up, returning to its earlier seasons will make each moment in the anime's epic conclusion even more fruitful as every loose end is finally tied up.