Yeah I had something like that happen to me. There were 6 of us in a tent sharing a bong. I take about 4 or five hits and then we all just start laughing uncontrolably for what seemed like fifteen minutes. Then we stop for awhile and I start feeling *really* paranoid. Everyone else continues talking and laughing, but I'm sitting off in the corner just staying quiet.

Slowly I start developing the thoughts that the people in the tent aren't real, but are just figments of my imagination. It was really scary, it almost got to the point where I was going to go up to my friends house to talk to his parents to calm me down. Luckily I didn't, and after I took some deep breaths I layed down in the tent and closed my eyes and it slowly went away.

Also for some reason lately when I get high it's like I'm in slow motion, anyone else get that :P