Bungie teased this particular egg for a while, leaving a bevy of little clues in their Q & A community posts. Fans knew the egg occurred on a particular day, and that it was somewhere in the Halo 3 loading screen. The second of the clues came from programmer Adrian Perez, now at Infamous studio Sucker Punch. When asked back in 2012 what his proudest moment was during his time at Bungie, Perez said, "Showing my wife the easter egg I put in the Halo 3 loading screen for her - the one that nobody has found."
Some two years later, Halo fan "Lord Zedd" somehow managed to find it, as you can see in the video above. Just imagine how Adrian got his wife to see the secret.
"Lauren, I know it's Christmas day and your birthday, and we've got all these things to do and the whole family will be here any minute. But maybe we could play some Halo for five minutes?"