Just before Stefan kills his dad, he realises the game: he can feel us, the viewer, influencing him. If you send him a sign from the Jerome F. Davies book, that's when he goes off the rails and commits murder. But if you tell him Netflix is behind the whole conspiracy, things get interesting.
First, you try to explain to Stefan what, exactly, Netflix is. This is funny, since he's a kid in the '80s and can't possibly wrap his mind around a "digital streaming platform." He goes to his therapist at his wit's end. His therapist is the voice of reason: why would anyone want to watch Stefan's life? It's so boring. That's when the fight scene breaks out. Yes, the fight scene! R. Haynes literally pulls lethal weapons out of her drawer and eggs Stefan on.
Two choices: do you fight the therapist or jump out the window? If you fight the therapist, you witness a wild action sequence in which Stefan literally goes fist to fist with his therapist and his dad, who eventually drags him out of the centre screaming. If you jump out the window, there's a fourth wall break: we pull out. We're on the Black Mirror set. The director storms over and tells the actor who plays Stefan that that's not what the script says to do. The actor insists he is Stefan, and the medic takes him away.
Even though there are other endings that are arguably better, I think this ending captures the true thrill and excitement of a project like Bandersnatch. As soon as I told Stefan the truth, I was enthralled. I leaned in. Stefan's computer tells him what Netflix is, and for a brief moment, it all feels like reality.
It feels like you really are watching and controlling an actual teenage boy in the '80s, like this moment has somehow ripped the fabric of the universe to make it all real. Plus, the fight scene and the fourth wall break are simply just fun and exhilarating! It's almost like Black Mirror lets things go truly off the rails and leans into the crazy. It's refreshing, and that's why I loved it so much.