Easter Egg 2:
Planescape: Torment
Skull: "Do you think we skulls can just *float* arround?"
Looks like a reference to Morte for me.
In BG2 you got to kill some flying skulls too <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
I don't think it's limited to a few RPGs tho.