First off, there is already one Ghoul in Megaton (Gob), but I'm sure you knew that. I have never before heard of this happening, but new bugs and glitches are popping up ALL OVER the Wasteland. Most likely this happened due to a mod, and really shouldn't affect your gameplay unless they're all Underworld Ghouls or something where the regular Megaton character's dialoge options do not open, and in stead they just speak general text where no dialoge box opens...
