1 Good Haken: {running up to the books on the table} There it is. Die Book of der Dead.
1 Monty: And no Hitler! Perfect.
2 Monty: [hieroglyphs]
3 {Haken returns through the vortex from the Death Star}
3 Haken: I'm back! Herr Doktor Jones! Herr Professor Jones! Und... who are you?! {staring at his döppelganger}
4 Prof. Jones: {looking at the two Hakens} Didn't you say everything would return to normal, Junior?
4 Monty: I studied archaeology, Dad! Not physics!

2012-08-27 Rerun commentary: Somehow, I doubt physics would have all that much to say about what happens when a good version of a Nazi form another dimension meets his real world evil counterpart either.

For this sort of thing you probably need some combination of Weird Science, Occultism, Metaphysics, and Luck.