Michael turns back to put the teacup in front of Crowley. It's still steeping, but he can take it from here. 

"Well, we're all here from different universes, anyway." At least, hopefully Crowley's gathered that much by now? "It stands to reason that it's possible for the same people to come from different alternate universes. Or even just timelines. I don't know that it happens a lot, but it's just as statistically unreasonable as you both coming and going together all the time." It's been obvious to him for a while that this entire thing can't be truly random. But there's no obvious way to manipulate it, so...