In general, MQs of the main game and expansions are the true canon, sides are however you want it and most often will be vague in the canon (if it's mentioned at all).

But, since OB is highly linear in the guild quests, what if the CoC really did do all that? If so, it's quite obvious the CoC suffers from heavy split personality disorder, which could lend more credibility of why Sheogorath wanted the CoC to become the new Sheogorath! TWIST! You were insane the whole time and pulled off so many different feats.

well, I'd imagine going through the oblivion gates would lead to a very bad case of PTSD. Dissociative identity Disorder might even occur as a result.

On top of having to defeat Meridia's pet, Umaril, and become Pelinal's avatar for a while, the very guy who would have episodes of uncontrollable rage and wipe off parts of the world.

Hmmm...a very credible theory, especially the part about split personalities, the DB side, the MG side, The FG side and the TG side (the four main guilds)

Overall it seems like a great way to get rid of the CoC. Similar to how the Nerevarine conveniently decided to go to Akavir just before the Oblivion Crisis.

If the CoC did all the guild quests, then he has Nocturnal's Cowl and no one will know anything about what happened to him in TES V. Personally, I don't like the idea of the CoC turning into Sheo, because his realm wasn't all that mad, just silly. Like how someone who's never really seen madness would expect it to be.(And it's strange how easily the three invaders to the realm go crazy) Plus you never did anything without purpose, and none of that was particularly insane(In the context of the TES universe of course).

Sheo showed the CoC what he expected to see.

I don't remember who said it, but somebody came up a few threads ago with a very interesting idea. yes, Sheggy is cursed Jyggalag. He wasn't, however, cursed by the other Princes. He was driven mad by the creation of the mortal world, which is unpredictability incarnate.

As for the rest, the Champion is either some kind of wierdo regent-madgod, the full madgod by reason of mantling, or just nuts as a convenient way to retcon the events of Oblivion completely. So he could be any of the three main options. Since this is a continuity-heavy role-playing game world, I guess it's up to each to iron his or her own small details out.

I'm working on a theory that uses both the 'went mad' theory and taking what Sheo says as true theory to create a huge, super Zombie-Theory. The good bits are genuinely good. There's just a few holes I need to iron out before I can put it to you folks. I should be posting it this weekend.

Can't wait! I love a good SI theory.

Yeah. Well I guess either way he will just disappear like Nerevar did. Still it should be interesting to see if Jyggalag turns out to be a big bad guy later on in the series like Mehrunes Dagon. Bethesda has given themselves a lot of storytelling options.

I'm under the impression that the true core of Sheogorath is the root system, or more accurately, the Fountainhead. Especially considering how the Font of Madness was used to infuse the Staff of Sheogorath (the Symbol of Office) with magicka, and getting rid of the contamination by Priests of Order down there was vital.

sheogorath is every thing, not just in the drinking water...

It's important because it is a symbol and the war between Jygg and Sheo was a symbolic one. After all, whoever controls the fountainhead, the source with which all power flows from the power sink of Sheo into the realms to stabilize it with Sheo's goody good-ness, controls the realm.

The whole story of Sheogorath just tricking you is a great idea, but I still think it's kinda lazy way out. Like saying "it was all just a dream" way and kinda makes you feel the whole SI story was for nothing except to get rid of COC.
Which brings to the next point that I do agree that COC should be stuck in SI (becoming mad there or lord of it or both whatever) so it is clear where he/she went in future games. I also hope we get to learn more about Jyggalag in the next installments.

I think that the COC is just a regent for SI.

Its my understanding that Sheogorath lured the champion into his realm to end the grey march. The Champion became the ruler of the realm, but not the madgod himself. I believe that he is a vessel for the true madgod to be born into again the same way he was born into Jyggalag, a way of ending the grey march permanently without Jyggalag re-emerging to destroy his realm again. If you will.

That's saying what Jyg said: he guessed that you'll slowly become Sheog, possibly.

I think Sheogorath chose the CoC, like said earlier the CoC has done different questlines whether acting as a mage or thief or warrior. He saw the unpredictability of the CoC and thought he would rule his realm the way he thought it should be ruled, with madness. The CoC does whatever is necessary to appease his own means, there is always some reward. Plus I'm sure going through the oblivion gates takes a tole on the body and mind, it is very possible the CoC could be insane to a degree. Or at least lacking in judgement.

I think Jyg also had an influence on Sheo (voices in your head), Jyg needed Sheo to be defeated to be set free. What better way then to offer someone power and people to rule over so that he/she will fight for you. There's that reward I was talking about. So in the end, the CoC doesn't become a daedra, but he becomes sheogorath, which is a title that carries power. You must be sheogorath to rule the isles, not a daedra. You can still act as a deadra though due to the extent of the power you are given. So I think Sheogorath is gone to an extent. Perhaps Jyg will be the next enemy since the grey march was just beginning. It didn't say when it would end, I assume that is with the defeat of all the other daedra. Maybe Jyg will need to be recaptured and cursed again.

hmm...I think as was said in the game COC became sheo...but still mortal...
I dont think thet he became mad...or he is crazy.It isnt matter... cause do you think thet you are normal...hmm

Jyg will not be an enemy...most likely he start war against Mehrunes Dagon cause he is chaos and...Jyggy is order...so they made to be together=)

Jyg seems to hate the other Daedra, apparently. Why else would they have imprisoned him unless they feared his disgust for them would turn violent?

Does it make any difference?

The CoC is mad whether he/she is 'really' sheogorath or not.

You could have an infinite heirarchy of mad gods each one tricking another...

He kept a library predicting their actions too. In addition, there isn't any sign of him ever employing the services of Daedra, rather he utilized mortals and the Knights of Order.