Technical issues when installing a new game on your PC is nothing out of the ordinary, but some Call of Duty: Black Ops 2 players were in for a surprise when they popped in the second disc of the game. The surprise was that the second disc contained EA's Mass Effect 2.
This has been reported by PCGamesN who in turn refer to Reddit, Steam and YouTube.
The reason for the mix up is unknown, but we're likely looking at a screw up at a manufacturing facility. The extent of the issue also remains to be seen. Users who got Mass Effect 2 on their second disc can use the activation key to download the full game over Steam, so they're not completely left in the dirt.