So apparently, some PC users for Black Ops 2 were installing their games, when they inserted Disc 2, and it was a Mass Effect 2 Disc. talk about your weird crazy shit. This was a post http://blog.bioware.com/2012/11/13/were-answering-the-call/
To be honest I'd have trouble deciding what to play.. go with Black Ops like planned, or follow the signs and wreck sum ME2. Rather cool though, very odd. I wonder who's ass got canned for that mishap lol