(A starter for @alabonshay!)
"As Stanley came to a set of two open doors, he entered the door on his left."
Stanley has forgotten how many times he's heard those words spoken in that order by that voice. Enough times that he doesn't need to be told to take the door on the left anymore, but the voice still feels the need to tell him. That's just how the Narrator is, though. Omnipresent, though perhaps not omniscient. Controlling, but not in control.
Stanley goes ahead and enters the door on the left, though. He has no reason to deviate this time around. Nothing in his gut telling him to go right instead, or to jump off any platforms, or to head down any dark and ominous corridors. Besides, it's not that he wants to listen to the Narrator this time around or that he has any particular gut feelings. He simply wants to see outside, even knowing it isn't real.
It may be the last time he sees the outside ever again, and in his yearning for freedom, he can't help but take whatever he can get.
"-2845- Stanley, have you even been listening to me? I swear, it's like talking to a wall with you sometimes. I don't know why I even bother."
Stanley presses his lips together and enters in the code behind the boss' desk, although he manages to resist rolling his eyes. He hadn't realized he'd been tuning out the Narrator. Everything is on autopilot this time around, it seems, and most of the time through the Story he doesn't even need to listen to the Narrator to know where he needs to go. It's the same thing every time, so what's the point?
The fireplace swings open, the Narrator drones on, and Stanley continues his march, onward toward the Ending he's reached dozens if not hundreds of times before.
Getting there is the boring part, and as the clank and clang of his shoes echo on the concrete floors and metal catwalks, Stanley begins to tune out the voice in the ceiling again.
The voice in the ceiling notices.
Meanwhile neither of them notices when something goes fantastically... different.
"-Stanley decided that this machinery would never again exert its- Stanley, you're just not listening to me, are you? Here you are, seconds away from your freedom, and you're acting like you're a walking corpse. I might as well be talking to one. I don't know why I bother with you sometimes, if I'm honest."
Stanley gives a small shrug in acknowledgment as he enters the door into the room with the Mind Control machine. He can see the blue glow from the enormous monitor just beyond the door. Here, he'll have to make his choice whether to turn the machine On or Off.
"Well, if you're so content with being dead already why don't you- .....What the HELL is THAT?"
Stanley comes to an abrupt halt, because he sees it too. Something is standing there in front of the controls. Something a lot bigger and bulkier than he is, and better dressed to boot.
Lacking any other reasonable way to respond to this situation, the office worker just stands there. And waves a hello.