Mine would be the first few weeks of playing graal classic. When I was following through a video to find all the hidden areas, I stumbled upon people acting? I was in the cave and they kept telling me to please leave because their friend died. I was suspecting that they were just acting out some scene, so I stayed silent watching what will happen next. Then they just kept telling to get out getting angrier when I didn't respond. They then just continued on talking how they will miss him.
It was weird since I could not tell if they were talking for real or not.

Next to that memory would be seeing a whole group of people using the same huge shield code. Just funny how people work together unintentionally.