I'm sure most of us have very memorable and special moments in this game, myself included, I've been around since 2008 and I get to meet a lot of awesome people and got to do a lot of fun things.
I remember once that me and some friends decided to do a sleepover kind of server in my house build, we pretend that we were hanging out and passing the time, sadly I can't remember who it was but it was me and two other friends, we talked about a lot of things and we saw the daycycle passing by up until morning, it was a fun time.
There was also once on an airport server, some friends gathered around to play together and pretend we were "professional" pilots, all I can say is that disaster happened lol.
And also on my older days of Blockland videos, some of them were really fun to make, I invited some friends over to act as characters in the video, we had to the same shots over and over until we got the best shot, one of the most memorable ones was the Jail RP which had more than 10 players acting in the same server, it was tricky to get everyone in position.