The code '0451' is somewhat of a running joke in games, particularly immersive sims. It first appeared in System Shock, although the zero was absent, and then it resurfaced again in System Shock 2, although it was now 45100. Dishonored, another Arkane outing, even featured the number, so Deathloop is just the latest to continue this gaming trend.
System Shock was developed by Looking Glass Studios and the door code to access their office was '0451'. It might seem innocuous now, but it birthed a long-running reference that would go from a silly nod to a sprawling in-joke among immersive sim devs and players. It resurfaced in Deus Ex as the code to open UNATCO Headquarters which is noteworthy because Harvey Smith was a game designer at Ion Storm at the time, and now he's over at Arkane as co-creative director, keeping '0451' alive.
It came back in Deus Ex: Human Revolution as the code to open David Sarif's office, in Deus Ex: The Fall as the code to Mikhail Kontarsky's hideout, and it appeared again in the Deus Ex book Black Light as Facility 451. After that, it surfaced in BioShock and BioShock 2 as the code for the very first locked door.
Two years later, Dishonored brought the original code back (451) to keep the first safe locked tight. You'll also find it in BioShock Infinite (the only code in the game), Alien: Isolation, Gone Home, Firewatch, Mafia 3, Prey, and Tacoma. It has had a long journey throughout the medium, and that journey will continue tomorrow.
"You find another door in the next room - this one can't be hacked, but there's a keypad next to it," editor-in-chief Kirk McKeand said in his Deathloop review for TheGamer. "You've played games like this before - Deus Ex, Dishonored, Prey - and they love references. '0451' doesn't get you in, but it does get you something."
Deathloop - Arkane's latest launch - features this long-running gag, and even sports an achievement to reward you for trying it. PCGamer editor-in-chief Phil Savage managed to clock it along with TechRadar editor Samuel Roberts. At this point, it's a gut response to try '0451' when you come across a keypad in an immersive sim, so when Deathloop launches tomorrow, be sure to try it out.