It's fair to say that more video games than ever come complete with their own multiplayer modes these days, if only because developers are utterly obsessed with keeping "engagement" as high as humanly possible, often in order to flog microtransactions and loot box nonsense to as many players as possible.
But it wasn't always this way, and in years gone by developers would often include secret multiplayer modes in games which could only be accessed either by entering a code, simply stumbling across them in-game, or completing the campaign and actually bothering the check the menu afterwards.
Despite how fascinating and often well-crafted these multiplayer modes were, the developers generally kept them hidden for players to either discover on their own or, more likely, read about online.
And though some of these modes were definitely rough around the edges - hence why they weren't actually advertised as paid-for features - they nevertheless added a ton of entertainment value to their respective titles, especially if you had a little brother or friend who was watching you play for hours on end...
Stay at home dad who spends as much time teaching his kids the merits of Martin Scorsese as possible (against the missus' wishes).
General video game, TV and film nut. Occasional sports fan. Full time loon.