Short answers, pulled from the story.
The first video game to feature cooperative play is Atari's arcade video game Pong Doubles released in 1973. This tennis doubles version of their hit arcade game Pong allowed two players to work together on a single screen.
Co-op games became particularly popular among operators of coin-op video games during the early 1980s as they had the potential to net double the revenue per game. Several early 1980s arcade coin-op games such as Wizard of Wor and Joust offered co-op play options.
Drop-in/drop-out co-op was pioneered by Gauntlet released in 1985 which came in models of two and four players for different locations. This trend was followed by Quartet Ikari Warriors and Rampage all released in 1986 which became high-earners for American operators.
The industry has settled on games that support up to four players as an informal standard due to historical arcade limits and human social factors. While there are no practical technical limits to how many players can be involved most games max out at four players to encourage cooperation within the group.
In 2025 cooperative games gained the derogatory slang term Friendslop coined alongside the complementary term Friendfarming to describe specific types of cooperative experiences prevalent in modern gaming culture. The terminology emerged to reflect changing attitudes toward how players engage with one another in digital spaces where quantity of friends may be prioritized over quality of interaction.