The "I Would Have Been Your Daddy" skull is the most difficult Easter egg to activate.
This skull alters the Marines' dialogue. It's on the Outskirts level and requires that you play in Legendary mode. The mission objective to watch for is entitled "Find the marines from second downed Pelican." When you complete the activation for this skull, the notification "I would have been your daddy" appears onscreen.
Some of these interesting audio tidbits have been recorded. For example, one of the marines has been recorded saying:
As long as we're standing here, I may as well write my old lady a letter. Cortana? Do you take dictation? Take this down:
Dear Mary, I miss you so much, stop. Will be home soon? stop. How is the dog? stop. Have you learned to cook yet? stop. Love Sergeant. P.S. I've met someone. Will be home soon for divorce. Bye bye. P.S. Do you think I could take the dog? Maybe not…think about it…write back.
Got that, Cortana?
The "I would have been your daddy" (IWHBYD) skull is in a room on a balcony, so you will need to get onto the rooftops to access the secret area. The room contains a Sniper Rifle and Sniper ammo, and if you're lucky (see "Spawning the Skull," later in this hack), it will contain the skull.
Figure 2-10. One way to get up onto the rooftops
Once on this ...