Kappa, very much like /s, is meant to indicate that the statement preceding it is not meant to be taken seriously. A sign of gentle trolling and mild provocation, Kappa is the most popular emote on Twitch by far – with its rainbow-colored version, KappaPride taking second place.
Kappa’s origins can be traced back to the early days of Justin.tv. John DeSeno – the man whose face would become a global phenomenon – was hired in 2009 as an engineer for the site. Tasked with revamping the chat of its gaming channel – the precursor to what would one day become Twitch –, he and other employees added their own faces as emote options. It was an easter egg that quickly caught fire.
Contrary to popular belief, the emote’s name does not, in fact, refer to the tenth letter of the Greek alphabet. DeSeno’s choice of phrase originated from his interest in Japanese folklore, where Kappa is one of many supernatural monsters, a powerful, turtle-like creature that lurks in rivers and lakes, pulling in unsuspecting passersby. Its grayscale, Twitch-based iteration is nowhere near this scary, of course.
You can also use Grey Face (no space) as an alternative.