Is There A Way To Get NPCs To Clip Through The Player?

[MajorDong]

I've got a story scenario that more or less needs to play out on the top floor. I can easily foresee situations where the player might really jam things up if he happens to be in the middle of the hallway or at the top of the stairs at inopportune times. I'd really love to be able to just turn him into a non-solid object that the other characters can just walk through.

Can this be done?