In case you missed it somehow, the excitement for Supernatural Season 11 is at an all time high with the promise of a return to the original Sam (Jared Padalecki) and Dean (Jensen Ackles) against the world dynamic and now, with Jared Padalecki teasing that we're finally going to get to see God making an appearance in the Supernatural universe as the brothers "take him along for the ride".
"I think [the Darkness] certainly opens the door for Lucifer and/or God to pop up. We’re certainly going back to that and going a bit more biblical and having our take on the writings that didn’t make it into the Bible." - Jared Padalecki
What exactly is God?
God as a figure in the Supernatural canon is hazy, typically described as an absentee father, he left heaven sometime before Castiel (Misha Collins) first appears in the show.
In his absence the angels plan to allow the Apocalypse to happen so that they can defeat Lucifer (Mark Pellegrino). At this point God exists to the angels in much the same way as he does to humanity, with some believing him dead whilst others (like Castiel) believe He still exists. This divide eventually leads to civil war amongst the angels.
Though we never see him directly he often interferes in one way or another to save the Winchesters, particularly during seasons 4 and 5 in the lead up to Lucifer's return. He's also brought Castiel back to life three times now, so we know there's a soft spot there.
Wait, I thought we already met God?
For a while now it's been a widely held theory in the Supernatural fandom that Chuck Shurley (Rob Benedict) is in fact God. Chuck is first introduced as a prophet who writes the Supernatural books, recounting events of Sam and Dean's life as they come to him in dreams. When they first meet he makes a joke about him being a God; at this point he claims no prior knowledge that Sam and Dean were real people and jokes that he determines their actions by what he writes.
Following the events of Swan Song, the heartbreaking season 5 finale which ended with both Sam and Lucifer locked in Lucifer's Cage, Castiel is revived by God and in turn heals Dean and brings Bobby (Jim Beaver) back to life. Dean is embittered at this point, believing that God chose not to save Sam from Hell, though Castiel claims God helped them more than Dean realises.
At the conclusion of season 5 we see Chuck dressed in white as he finishes writing the book about Dean's Impala, the entries into which formed the narrative spine of this episode. In a voice over Chuck says that he believes the brothers have passed a test set for them by God as, in an epic fight between good and evil, Heaven and Hell, they did not take sides but instead chose family.
Chuck says that ending are hard, and never perfect, but reminds us that nothing ever really ends as he vanishes with a smile. This led many to believe that Chuck is not just a prophet, but rather the physical manifestation of the entity known as God.
Later, in season 8, whilst the brothers are discussing prophets, Castiel says that Chuck must be dead as there can only be one prophet at any one time, and Kevin Tran is the current one. However we see Chuck later on in season 10, when he appears at the conclusion of the meta-episode "Fan Fiction" at the end of the play - prompting further speculation that this is evidence of his divinity.
So why would God show up now?
With the brothers now facing the pre-Biblical horror known only as the Darkness, they're going to need help from the universe's most powerful entity, the one who locked the Darkness away in the first place.
Following on from Padalecki's comments there has also been speculation that Lucifer himself will be let out of the cage to help push the Darkness back, for its presence threatens everyone and everything - good and evil alike.
It would certainly be interesting to see Mark Pellegrino's wonderful creepy Lucifer returning, though I don't imagine the Winchesters will be too happy about that.