Some copies of Call of Duty: Black Ops 2 have Mass Effect 2 on the second disc
Gamers on the Steam community forums, Reddit and the Call of Duty forums are reporting that when they try to install disc 2 of Call of Duty: Black Ops 2, they instead get Mass Effect 2. So that's what Treyarch meant when they said they were adding moral choices to the campaign.
Early reports were confirmed when PCGamesN discovered a video by zeroiez (embedded above) showing him inserting a CoDBlOps2 disc into his machine before getting a prompt to install BioWare's Mass Effect 2 instead.
Exactly how an EA game ended up in an Activision case is uncertain, but it's possible the two publishing giants contract the same company to produce discs, and there was a disc image mixup at the factory. We've reached out to Activision for comment.
So far the error seems to have affected a relatively small number of people, but if you're one of them your best bet is to use your CD key to download the game directly from Steam instead. I hope your internet is up to the task.
Meanwhile, we've got Martin hard at work playing the real Call of Duty: Black Ops 2 for our review. He's just gotten to the bit where you meet Garrus.