"Yeah... But I guess technically, from our individual perspectives, we're just...us. Under normal circumstances we wouldn't even consider the potential of an entirely different version of ourselves- this is all very abnormal to begin with."

Donnie wonders how his other iterations would be. Would they have handled things here better or worse than he has? It doesn't really seem like something to compare and contrast with so far as he can figure. The other turtles of other universes seem to have different experiences, and from what he's seen, he can already figure there's at least two other different versions somewhere out there.