Enter it at the Cerebro Files menu, press Up, Up, Down, Down, Left, Right, Left, Right, Start
Unlock Danger Room Missions
There are eight danger room missions. You unlock the first three as you play through the game. To unlock the other six danger room missions, you must collect all Sentinel files and Weapon X files with each character.
Wolverine Danger Room missions
Enter it at the Cerebro Files menu, press Down, Down, Up, Up, Right, Left, Right, Left, Start.