Short answers, pulled from the story.
The first video game to feature cooperative play arrived in 1973 with Atari's Pong Doubles. This tennis doubles version of their hit arcade game Pong marked the beginning of an era where players could work together rather than compete against one another.
Gauntlet introduced drop-in drop-out co-op in 1985. This feature allowed players to join or leave the game at any time without disrupting the flow, which became a standard for future titles.
The Nintendo 64 released in 1996 featured four controller ports as a standard. This hardware advancement allowed for more complex cooperative gameplay on home systems compared to previous generations.
Killing Floor reemerged as a co-op wave-based survival game mode in 2005. Originally a total conversion mod for Unreal Tournament 2004, it brought the co-op wave-based survival game mode back to the forefront of the genre.
Sony Computer Entertainment America introduced the SimulView feature set in 2011. This technology renewed interest in 3D Television by using alternate-frame sequencing to present each of two couch co-op players with their own 2D full-screen image on the same display.
The derogatory slang term Friendslop emerged in 2025. This term refers to non-MMO games such as Lethal Company, R.E.P.O., and PEAK which have become popular for their cooperative mechanics.