It turns out that if you load the game up on Christmas day (or change your Xbox 360 clock to make your machine think it's Christmas day), then press both Xbox thumbsticks down, the loading screen shows a new view of the eponymous Halo space ring, complete with a scrolling message reading, "Happy Birthday Lauren". The text, it seems, was included by one member of the development team, Adrian Perez, who directed it to his wife and never expected it to be found. 

 

Full article here

 

And here's the video of it in action: