Assassin's Creed fans playing Final Fantasy XIII-2 will be able to dress protagonist Noel like Ezio Auditore in Assassin's Creed: Revelations using a DLC costume. Square Enix Europe says the costume is coming "soon". There's currently info on when the costume will be coming stateside, but based on other DLC, it will likely come out around the same time.
This isn't the first Final Fantasy XIII-2 franchise crossover DLC costume. Square-Enix worked with Bioware to bring commander Shepard's N7 armor from Mass Effect 3 to the game. The N7 armor is available today in the both North America and Europe.