Theodore Roosevelt/WMG

Theodore Roosevelt had blood ties with the Belmont Clan.
That's why Death had to take him while sleeping, for if Roosevelt had been awake, Death would've lost.

Theodore Roosevelt was God's prototype for Chuck Norris.
When the Lord saw the power of His creation, He knew that He could not let it end there. So He spent years, trying out just the right combinations of Awesome and Cool, until He finally gave us the Texas Ranger himself.
 * Naw, man, Roosevelt is a distant ancestor to Chuck Norris, only direct bloodline can pass down awesome like that!
 * Additionally, the flaw in this argument is that it assumes the latter person to be superior to the former. Teddy would kick that cowboy's ass.
 * More so Teddy Roosevelt was so awsome that to be contained in this world he needed to be mixed with less awesome, thus Chuck Norris
 * Super Prototype?
 * Alternately, Chuck Norris is Roosevelt's reincarnation.

Theodore Roosevelt is either God, or at the very least a god.
Extremely charismatic? Check. Ridiculously larger-than-life figure? Check. So badass as to be borderline unbelievable? Check. Possibly immortal? Double check. Really, I'd be more surprised if this wasn't true.

Theodore Roosevelt is still alive.
Death was merely able to knock him unconscious for a while. TR slumbers underneath Mount Rushmore with the Rough Riders and shall awaken to save America in its hour of need.
 * Theodore Roosevelt wanders the Earth like Cain from Kung Fu
 * Cain from Kung Fu wanders the Earth like Theodore Roosevelt
 * Theodore Roosevelt Gentleman Adventurer still ventures this world’s last frontiers, in an endless quest of discovery.
 * This world’s last frontiers? The final frontier is space! When humanity reaches the stars they’ll find Theodore Roosevelt waiting for them.
 * No, he discovered the secret to time travel and is currently in the prehistoric era hunting dinosaurs.
 * And he is thus responsible for their extinction, and allowing mankind to evolve

Theodore Roosevelt was actually an identity of the God-Emperor of Mankind.
Search your feelings, you know it to be true.
 * The God-Emperor of Mankind simply isn’t awesome enough to have been Theodore Roosevelt.

Theodore Roosevelt was one of the Unknown Primarchs

 * A veritable demigod, sent back through time in order to lead humanity, a great burning beacon of virility that all males would strive to imitate, paving the way for the all-out MANLINESS that is Warhammer 40000.

Theodore Roosevelt died because he wanted to.
Let's be serious here, he could've kicked Death's ass in his sleep. The only reason he died was because he was bored with this world and wanted to see the afterlife (and pwn it), so he went without a fight (in his sleep because Death would've been too afraid to show up if he was awake).
 * Confirmed, more or less. Given that one of his sons died only a year before his death, and his health had failed in the interim, its all but certain that his was a Death by Despair that happened more or less entirely because, with his son dead, he didn't really see the point in living anymore.

Theodore Roosevelt gave his infamous Big Stick to America.
Remember that strip with Canada where he had a big stick lying around? That used to be Teddy's. Since he couldn't trust it to mere humans, he decided to give it to the only one he saw worthy of it: Alfred Jones/America. And it wouldn't it be surprising if some of his enthusiasm rubbed off on the Nation.

Theodore Roosevelt was a scion of The Erlking.
Think about it. He loved hunting, was a total badass, and really only cared about conservation so he would always have something to kill. It's either that, or he was like the Summer/Winter Knights, except for The Wild Hunt.

Theodore Roosevelt isn't in heaven.
Two reasons: One: to put the fear of GOD back in Lucifer. Two: God himself worries over his position while the man is around.
 * He must've taken over by now. Hell will be awesome.

Theodore Roosevelt wasn't taken in his sleep.
It was a trap for Death. He was waiting for Death and is now in the afterlife hunting the bastard for taking his family members from him.

Theodore Roosevelt was our world's embodiment of Spiral Energy.
Every reality/world/universe has one. So now the Guessing must be on WHO REPLACED HIM!
 * Chuck Norris, of course!
 * ButRory Williams replaced Norris
 * He's still the embodiment of Spiral Energy, much like  The real question is who's our Anti-Spiral?
 * The reason we don't know - and will never know - is because Roosevelt clearly had already finished off said Anti-Spiral counterpart well before taking office. It was just a warmup for him, really.

Theodore Roosevelt is the time-displaced future man-child of Adam Savage and Jamie Hyneman.
Because he just looks like what you'd get if Adam and Jamie finally gave in to the smouldering passion that runs beneath their every moment.
 * ... You've been reading too much Yaoi. Obviously, Jamie/Teddy are the same person.

If the Earth is ever invaded by aliens, the US government's secret contingency plan is to awaken Teddy Roosevelt

 * He is incapable of actually dying. He is merely in a deep state of hibernation. That's what Area 51 actually is: TR picked a cave in the Nevada desert as his hibernation spot (because he loves the western landscape), and the US government built Area 51 around that cave in order to keep it a secret. Eventually when an alien invasion occurs, the government will awaken Teddy. And he will rise out of the desert, assemble an all-new group of Rough Riders, and will royally kick the aliens' collective asses and send them crying back to their home galaxy. And it will be utterly awesome.
 * Close. The cave is actually the American portal to Avalon, where Teddy went to recover from the emotional wound of losing his son in the War, after promising to return again in America's hour of need. Area 51 was set up around the portal so that when he does return, there's a base right there to update him on the situation and provide supplies and personnel.
 * And some more detail on the part about Teddy's new Rough Riders: It is very likely that Teddy will recruit Chuck Norris, Robert Downey, Jr., Samuel L. Jackson, Bruce Campbell, Bruce Willis, Sylvester Stallone, and Clint Eastwood to be among the members of his new Rough Riders. Because a badass leader like Teddy Roosevelt deserves a Badass Army.

He'll come back as a White Lantern
And he'll light our darkest hour

He killed and replaced death.
And he is now the Grim Reaper.