I just noticed something

[slims]

Now this may be dumb but here goes. In as the world turns Eminem says he has a twin, could evil twin be an expansion on that? Don't mind me, I've got to go back to bed.

[csw621]

I always felt it was more of a reference to Bad Meets Evil. But you're definitely right about As The World Turns being one of his earlier examples of dealing with multiple identities ("Oh my God it's you, not again!").

[Just Silver]

Reach

[UnoDeuce]

Nah, I mean of course he's talking about the same thing, about his "evil twin" (Slim) doing fucked up shit just to shift the blame but he references that a lot throughout his career.