I'm trying to recall various things from old Casey, aside from the obvious like Wojak and Polandball.
Of the personalities, I most vividly recall Fatczech/Newsczech, Nordamerikano (lernu esperanto), the one Iranian who ended up as a moderator, and DyslexicBrit.
Wojak is the site's biggest cultural contribution, even though most non-Bernds have no clue about it. It's surreal to think of having been on KC when it was still basically confined to it with only a tiny bit of spillover to 4chong's /int/, having no clue at the time it would become one of the most defining and enduring features of global internet culture. Gotta wonder what Wojak (the Pole) thinks, his creation and its permutations having attained worldwide fame by accident yet himself remaining completely unknown to the world.
Polandball was popular for a time, peaking in the middle of the previous decade. Had its own subHabsgelesen, and you might occasionally see it posted on social media. But it quickly fizzled out, I assume more or less at the same time as KC itself, and now seems very much dead.
Other than that, I remember a bunch of memes from cross-pollination with Finnish imageboards, primarily Ylilauta. Spurdo spärde, "Grease pay denbts", KC-tire Stallman, Spede Pasanen (Assburger). There was Proofster during the 2014 invasion of Crimea that was a KC original, and Remove Kebab too, but can't recall much else.
IWO threads, those were always very good and interesting.
Post ITT anything related to KC of the previous decade.