So, Ian McShane is joining "Game of Thrones," and everybody is freaking out, because:

(A) It's Ian McShane!

(B) He's listed as a mystery role, and there's nothing we love on "Thrones" more than a good ol' fashioned mystery! (Answers are cool, too.)

(C) Did I mention that IT'S IAN MCSHANE?

Look, you don't hire foul-mouthed Al Swearengen for an all-new HBO gig unless it's a big one. Combine McShane's instant name recognition with the weight of "mystery role," and you're left with the reality that whoever he's playing, it's going to be a big deal.

How big of a deal, though? Depending on the identity of McShane's role, it could be REALLY big, or just makes-you-super-happy big. Here are a few of the possible figures in Westeros lore we could see McShane playing:

Theon Greyjoy's Uncle

The consensus pick for McShane's "mystery role" seems to be Euron Greyjoy, brother of Balon, and the captain of a ship called Silence, crewed by people who have had their tongues ripped out by Euron. So, he's basically a really nice guy.

Euron, also known as Crow's Eye, becomes a major force in "A Feast for Crows," the fourth book in George R.R. Martin's series, but it's still not clear just how major he'll be in the grand scheme of things. But with reports of the Iron Islands gaining prominence in season six, and if McShane is being called upon to bring Euron to life, one can easily see the Crow's Eye becoming an important player on the show.

Daenerys Targaryen's Father

As suggested by MTV's own Alex Zalben, what if McShane isn't playing someone from the present of "Game of Thrones," but rather the show's past? Season five dabbled in flashbacks via Cersei, and if season six follows suit, perhaps we could get a glimpse at the infamous Mad King's final days ruling over Westeros. Few actors could bring that Targaryen madness to life quite like McShane.

Ned Stark's Old Friends and Foes

Sticking with the flashback theme, what if McShane defies our expectations and takes on a more heroic role? There are few figures more legendary than Ser Arthur Dayne, one of the knights who stood their ground against Ned Stark at the Tower of Joy, considered by many to be a key moment in Westeros history. (See: R+L=J for more.)

Another person at the heart of the Tower of Joy (and thereby R+L=J) is Howland Reed, father of Meera and the late Jojen. He's one of Ned's last living allies, and potentially the only person alive who knows of Jon Snow's true parentage. Fans have been waiting for him to emerge in the books for, well, FOREVER, and since "The Winds of Winter" still isn't here, it's possible that Howland will finally emerge in the next book, and we just don't know it yet. How insane would it be for McShane to not only appear on "Thrones," but to appear as such a long-awaited character?

Very. The answer is very, very, very insane.

Samwell Tarly's Father

Lord Randyll could have a role to play in season six, given that Sam himself is going to be riding close to home on his way to Oldtown. It would be a small part for a guy like McShane, but (A) there ARE no small parts according to Claude Dumet, and (B) McShane ripping into John Bradley-West would be a thing of pure gold.

The Night's King's Father

Is there a White Walker boss behind the White Walker boss? If so, hard to imagine anyone more badass than McShane taking on the role of the main main villain of the whole series. Then again, hard to imagine McShane's signature line delivery popping off the lips of a White Walker, but stranger things have happened.

Speak of stranger things, how about the STRANGEST thing? What if McShane is playing…

Jon Snow

Maybe Jon warged into McShane before he died okay fine no.

Besides, here's who we all REALLY want to see McShane play…

Al Swearengen

I don't care how this happens, just turn season six into a full-fledged bonus "Deadwood" season for all I care, as long as the Gem's proprietor rides again.