Contrary to what you probably thought, yes, this is a game.
The rules are pretty general. One person will post what could ruin the Halo movie, by saying "The Halo movie will be ruined if [insert soemthing here]".
The next poster has the choice to either improve upon that statement, or try and top it by simply posting a new statement, completely unrelated except that it begins with "The Halo movie will be ruined if" and is also about what could possibly ruin the Halo movie.
If the poster decides to improve the statement above him, by adding to it and generally making it more ridiculous, and then the next poster improves that, and then the next improves that...well, it'll just become very ridiculous. If a poster just posts a new statement, a new chain is started. If you decide to improve a statement, you can only improve the statement directly above yours.
So, basically, it goes like this:
The Halo movie will be ruined if they changed the Elites to Apes.
The next poster has the choice to either make a new statement, or improve the last one, like this:
The Halo movie will be ruined if they changed the Elites to radioactive Apes.
The poster after that has the choice to either improve the radioactive Apes statement, or post a completely new statement to possibly be improved by the next poster.
The Halo movie will be ruined if they changed the Elites to radioactive Apes.
The Halo movie will be ruined if they insert a sexy dance scene.
I can only imagine how some of you sick, sick people could improve that. Sick, sick people. With that said, keep things appropriate. Just, don't be stupid.
I'll start things off. The Halo movie will be ruined if the music is done by Randy Newman.
The Halo movie will be ruined if MC becomes aware of a lost son and must send him on a quest in the first five minutes, because the original MC is on his deathbed. Because of AIDS.
The Halo movie will be ruined if instead of landing on a giant ring that can blow up the world, it follows the adventures of Jesus and his woodland friends.
The halo movie would be ruined if the master chief came out od the clost at he begining and tries to kill a brute with a giant pink feather. (actually I would love to see that lol)