Re: I thought that episode was original, until...
I was just thinking the other day that an episode of Buffy the Vampire Slayer is a remake of "The Enemy Within." In "The Replacement," Xander gets split into his confident and sniveling sides.
More like the capable confident adult he was actually becoming and the man-child version of himself (full of doubt, jealousy, fear) he was afraid he truly was deep down and could never leave behind.
"There is no reason why good cannot triumph as often as evil. The triumph of anything is a matter of organization. If there are such things as angels, I hope that they are organized along the lines of the Maffia." - Winston Niles Rumfoord.