I like to call Psychotic Paul because sometimes people think I'm trying to say a bad word when I call him Pssy!

I generally call them what I call them online. As for whether I use their real name or not, that depends on who it is.

Para exampla, I dont think I'll ever call peegies "Mike" unless I'm introducing him (Which might actually happen!)

Usually though, i prefer to give someone a personalized nickname, so whether they are called by their real or screen names has a lot to do with how nicknamizable those names are.