"I wonder if the developers thought of this... oh man they did this is awesome"
So a few months ago I was playing the NES SRPG Just Breed, which was fairly enjoyable, rather generic characters and story aside. One of the things that kept me hooked in the game was the way the game would occasionally reward me for talking with every character over and over again and experimenting with going to different places, even places I'd already been before.
There's one town on a body of water where the only way to proceed is to go through an undersea tunnel, but the tunnel is blocked off by a dude because it's privately owned by a shipping company. After a short NPC talkan quest to get permission, you go back to the dude, who apologizes profusely and moves one square to the left, toward the ocean. If you speak to him again, he apologizes some more, and then moves one square to the left again. If you talk to him enough times, he'll fall into the water and die. He's kind of a douche to you earlier, to be honest, so it feels pretty rewarding to send him to his death.
My favorite things happen after you and two of your PC generals get poisoned. The poison makes the characters walk erratically and have garbled speech, and during battles, there's a chance that the poisoned general will have a spasm, which causes the general and his troops to automatically move around and attack instead of being controllable (this is usually bad, because the AI is not great). There's a doctor who can cure you in the next town over, so you're supposed to slog through one battle between the two towns and then get healed.
However, once you get there, there's nothing preventing you from skipping the doctor completely and proceeding to the next town! The battle you fight between them is kind of tricky, but still fairly manageable while your characters are poisoned. Normally when you're in a town, your generals wander around and you can talk to them for help with what you're supposed to do, but if you don't cure them, they (incoherently) plead for you to go back to the doctor. Additionally, the NPC that leads you to the next area can't understand what you say and refuses to take you.
In fact, it's possible to skip the area you're supposed to head to next, fight your way through an even harder battle, and make it to yet another town before you're forced to go back and get healed! You even get new garbled messages from your generals.
But there's more! In the town before the one where you get poisoned, one of your generals has a scripted event with a townsperson. The event gives you some plot, but it's not necessary to complete the game, so you can skip it. If you do so, get poisoned, and then go back and trigger the event, the lines of the person you're talking to remain the same, but your general's lines are total garbage. It's fantastic.
Some of the more prominent examples of the dev team thinking of everything are the Mother series (SWAMP BICYCLE, hidden background music that doesn't appear in the sound test that only plays when you return to an out of the way location long after you've finished it) and NetHack (a unique message for changing to another species, genociding your original species, and then quitting the game before you change back, why not). What are your favorites?
Jam it back in, in the dark.