Had the pleasure to raid for the first time in Karazhan. Back in 2.4.3, my guild was very casual, just a bunch of friends. So it was rare to get a group of 10 people willing to run it, and them being geared enough. That's how I got in, 1 or 2 days after reaching level 70 on my warlock. I knew jack about raiding, stats, rotations, I was carried essentially. But it was so much fun! And we were there the entire evening, from like 18:00 to 00:00. We were progressing slowly, and reaching Malchezaar was a relief.
His emotes are still one of my favourites: "You face not Malchezaar alone, but the legions I command!".