Stefan

Stefan is a radioactive Ghoul who was captured, imprisoned and experimented upon by the mad scientist, the Surgeon. He is caged inside the CEO offices of the Red Racer Factory in the Capital Wasteland.

Viewing Stefan while wearing the Ghoul Mask (received via the Tenpenny Tower quest) results in him regarding you without hostility as any other ghoul does. Besides his name, not much else is special about him, except on certain saves where he seems to prefer to squatting in an awkward position over a dead wastelander.

Killing The Surgeon will make Stefan become hostile, even while wearing the Ghoul Mask.

NOTE: However on some playthroughs on the PC and PS3, this did not happen. If you make him hostile by killing the Surgeon(and wearing the Ghoul Mask), and do not loot the Surgeon, then leave the CEO Offices and then come back, he will return to non-hostility.