EIGHT NEW ZONES!
Go back in time with me to 2006. The Naughty Sorceress showed up at level 11 and we fought her wearing the Furry Suit. Nobody had ever heard of the Holy MacGuffin or the Island War. Semi-rares didn't exist. There hadn't even been a spleen familiar in Mr. Store yet.
For months, Jick and Skully had been talking about an upcoming injection of content to the game. It was excitedly known as EIGHT NEW ZONES, and the community was abuzz. If I remember correctly, there was a countdown timer placed on the front page--though maybe I'm confusing that with another big change to the game.
We all knew it was coming, but there was surprisingly little spoiled about it. There was a long rollover the night it was launched (September 19, 2006). I saw the announcement heralding the arrival of the EIGHT NEW ZONES, and eagerly went exploring--only to find that the EIGHT NEW ZONES weren't just dropped onto the map.
Somebody in chat mentioned a new adventure in the Haunted Pantry. We checked it out. And as the night continued, this wild new zone, Spookyraven Manor, unfolded. There were keys! There were dusty bones to collect! There was a staircase that nobody could figure out how to climb! And all of this was extra exciting to me because Spookyraven manor was a spooky zone, and the modern elemental system, where monsters could have elemental alignments and weaknesses, had only existed for about nine months.
It was the single biggest injection of content into the game that I'd experienced to date, and I stayed up so late exploring it.
The rollout of NS13.
If you're new to the game and weren't around in *cough cough* 2007, I'm not sure it's possible to convey just what it was like back then.
Jick spoke of NS13 with the same sort of optimism he has these days when he talks about Standard. NS13 was going to shake things up. It was going to radically disrupt everyone's strategies. Speed ascension was going to change. Jick was unhappy with how optimal speed ascension required so much fiddly bullshit, as well as with how fast the game could be completed. NS13 allowed him (and the rest of TPTMBG) to nuke the fiddly bullshit and lengthen the game considerably--which would allow them more freedom in creating future content. They could make new things without stressing over how many turns they shaved off a run.
Some people were pissed about the impending changes; some people were excited. We were all, I think, filled with trepidation of one sort or another. When the site went down for rollover on NS13 launch night, I installed a Firefox plugin and auto-refreshed the page every minute. My clanmates and I babbled excitedly in an IRC channel, unsure what to expect. When it finally came back up, KoL was a new game.
If you want a snapshot of KoL right at that turning point, take a look at the NS13 FAQ. The April Fool's joke from earlier that year also give a sense of what people's anxieties were.
The rollout of Hobopolis was another big event that sticks in my mind. KoL is such a better game now than it was some eight years ago, and it's been really cool to be here for most of the changes.