Something that totally shocked you learning it or realizing it. I might be using the wrong wording here, but ill give you my example:
In Ocarina of Time, we all know the Triforce was cut, or otherwise not something you get in the game, save for in the cutscenes towards the end. BUT - did you know you can actually go find it and see it in the game?
If you have a Gameshark, turn on the levitation code. Go go Zeldas Cortyard in the room where she is, and fly over the wall. When you fall, you’ll land in a pool of invisible water, and underneath the center of the room with the flowers, look down - there it is. Can’t interact with it, but you can see it, and i choose to believe putting it in that exact spot was intentional for lore reasons.
What do you got?
If you’ve completed enough endings of Nier Replicant/Gestalt you’ll already know the twist at the end of Nier Automata, but less known is that the triggering event of Nier’s plot, White Chlorination Syndrome, is introduced by ending E of Drakengard, where the Japanese Air Force shoot down a dragon that just killed a god in a dance off.
This means that the reason you can find the Drakengard weapons in the Nier games is because Caim was carrying all 65 different swords, axes, maces, hammers, spears, staves, and polearms on his person when he was blown to fucking bits by an air to air missile, scattering them across Tokyo.