After choosing to be Anti-Registration, you will go on a mission to stop the Pro-Registration forces from destroying your shipment of weapons, and later, save Cable. There is a room you cannot access due to electricity, and Captain America will say to find "someone you can send in" there is a robot on either side of the door. Activate one. He will step inside and explode, allowing you to access the room. After you leave the room, activate the other robot. He will follow your team and help you fight the enemies. As long as he is not destroyed for the rest of the mission, after you save Cable the robot will get a short cinematic, where he will dance before self destructing.