Halo--The Legend for a New Age

Does the Halo triology have any subliminal messages? Secrets? Mysteries?
How did this multi-million-dollar, award-winning, blockbuster game get to that status? Why is Halo so popular? 

This is the first part of a youtube series which explores these questions and more.

 Does the Halo video game trilogy have subliminal messages? Reversed messages? Secrets? Hidden symbols? And, what do they mean? Also, does this video game have an agenda?