Todd in the Shadows/WMG

Todd is Brad the pianist.
He never shows his face so that people don't recognize him. Likewise, when he appears at the school he never speaks so that people don't recognize his voice.
 * Todd is pretty vocal about his hate for Glee so.....

Todd in the Shadows is really a Hunter.
Just look at him! He looks like one and dress like one. He hides in the shadows in order to hide his zombie nature from us. After he's done talking about the latest Lady Gaga song or whatever, he crawls out of his window and pounces on an unsespecting midnight jogger.

Todd In The Shadow's face will be revealed for the third-year anniversary special.
It just makes sense. It would also be a great dramatic twist like with 3D Lee.
 * Or, alternatively, he'll stitch screening into his hoodie.
 * Jossed, like with his Magfest appearance, he was wearing a black cloth over the top half of his head.

Todd made an appearance in Arcade Fire's "The Wilderness Downtown."
While watching, take a close look at the "protagonist"...Gray hoodie? Check. The Faceless? Check. Seen in shadow most of the time? Check. Sound of a piano in the background? Check. Presumably, the reason he's running is that someone tried to force him to listen to BIEEEEEEEEEEBERRRRRRR.

Todd in the Shadows is actually Justin Bieber
This only derives from the fact of Todd and Bieber both wore gray hoodies. But here's the thing, Todd is the bitter adult version of Bieber and the reason he gets so mad is he regrets being that whiny kid that couldn't sing. He got some piano lessons and learned how to sing, and presumably got a TARDIS somehow to travel into the past and rail on pop music, including his shameful career.
 * ...Which is why we never see his face!
 * As explained here
 * Also, he mentioned having previously been a big fan of Usher...J-Bieb's producer!
 * And creepily, I once saw a short little MTV promo featuring Bieber playing the piano...

Todd in the Shadows is actually Tee Hee Tummy Tums
A.K.A The most beautiful man in the world. Hence why he must forever dwell in the shadows, lest he be crushed beneath a mass of swooning fangirls and fanboys eager to tear off a peice.

TITS is the guy who leaves Rube the envelope.
The sweatshirt is so he can be shot from behind without arousing suspicion. Alternatively, he might be Father.

Todd In The Shadows is BRIAN BLESSED
...it could happen.

Todd In The Shadow is Ke$ha
An alternative to his being Justin Bieber- Ke$ha, years later, drops out of fame utterly wasted and uncared about, however she is kidnapped by a team of mad doctors who completely alter her body, voice and remove the effects of years of alcohol consumption from her system. She escapes then broods on her lack of talent and wasted life. She learns how to play the piano, finds a TARDIS and uses it, adopts a secret identity and becomes a pop song reviewer, in the hopes of making her former self and pop music associates rethink the music that got them executed by the Seahorses in the future.
 * That scenario... is so... epic.

Todd In The Shadows is a former one hit wonder from the future
Going off above guesses, Todd is a former one hit wonder from the future. In fact, he might even be a one hit wonder who's one hit was a cover. He did say in his Top 10 Worst Songs of 1987 he felt sorry for those types of artists. Unable to deal with the fact his only claim to fame was off a cover of some "old" song instead of an original by him, Todd travels back to our time period to review "current" pop songs. His one hit might even be one of the songs he's reviewed.

Todd is an albino
He wasn't kidding about being black. The reason for his decidely light complexion (from what we have seen) is that he is albino. This also explains why he has to be covered at all times, because albinos have very sensitive skin.
 * Jossed: He is, at least, Ambiguously Brown as further footage has shown.

Todd is Hiro Protagonist.
Apparently he's both black and Asian-American. Hiro is of African-American and Korean-Japanese ancestry. There's also the sword he uses to commit harakiri with...

Todd in the Shadows is really Monster in the Dark.
...it could be explained somehow.
 * AWESOME.
 * The Monster is Obfuscating Stupidity when it's around people like Xykon or Redcloak who it knows to be smart and cunning, because it also knows that if they should learn that the Monster is smart, logical and willing to use its powers for reasons it wants to, it might end up dead, enslaved or on the run. It occasionally uses its powers for things it wants, such as teleporting O-Chul, but whenever it does so it continues to Obfuscate Stupidity so nobody catches on. However, occasionally things become a little too much for the Monster, so it teleports to Earth and lets off steam in the most harmless way possible... reviewing pop music. To cover its tracks, the Monster changes shape to Todd, but because of habit, it/he always wears the hoodie and stays in the shadows. So far it's worked, but God knows what'll happen if anyone else on Earth (or in the OOTS-verse) finds out...
 * Fanfic. Now. Please.

Todd is the next regeneration of the Master.
He's been American before, and kept the liking for hoodies. After his last disastrous outing, the Master's taking a break dissecting the worst parts of Earth culture.
 * Furthermore, the piano is his TARDIS.
 * No, it's the Event Synthisiser from Doctor Who Classics #7!

Todd is Elvis.
Hey, it could happen.

The next review will be of DEV 2.0

 * From how he reacts to seeing them and his line "One crisis at a time" it would not be a stretch.

Todd will eventually marry Obscurus Lupa

 * Just because "Obscurus in the Shadows" makes so much sense as a name.
 * Lupa is already married
 * ... OT 3?
 * We've never seen Todd's face, maybe he is her husband. His Lupa-themed desktop wallpaper isn't a sign that he's a crazy stalker, just a devoted spouse.

Todd has red hair
Or some other recessive hair}} color like dirty blond.
 * Jossed. The Head video showed his hair is black/dark brown. (Thought I supposed it COULD be dyed.)
 * Confirmed on his Twitter.

Todd is in danger from The Slender Man
In his review of Chris Brown's "Deuces", there's a bit of static just before the "Valentimes" line. It's just for a split second. This digital distortion is similar to the distortion in Marble Hornets and Everyman HYBRID. Maybe Slendy's a fan of the songs Todd bashes?
 * Slender Man does not approve of the hatred of Take It Off. Slender Man liked Take It Off.
 * There's a theory that wearing a mask keeps Slendy from finding you. This is why Todd never shows his face.

Todd is Alex Mercer from Prototype
He has a hoodie, he recently came down with MRSA (often pronounced 'Mer-sah') he survived it, suggesting that he's resilient and refuses to die. He also goes on a Roaring Rampage of Revenge whenever people make extremely terrible pop music (e.g. Deuces, but also in 'Soul Sister' when he says that he will hunt down the lead singer). Gaga isn't the only monster who is mutating quickly.
 * Wellll....MRSA itself isn't a killer. It simply fosters infections and is resistant to antibiotics. However, the staph infections that often appear in its wake can be lethal, so "resilient and refusing to die" both still apply.

Todd is The Shadow.

 * The Shadow?
 * The SHADOW!
 * The Shadow...

Todd is a nazgûl.
It was said in the forum, and it's epicly awesome, so I added it here.

Todd will dress up like a normal person at Magfest and will not reveal to anybody that he is Todd In The Shadows
It will be a way to keep himself anonymous. He might also go by a different name or Todd might just be his stage name. He might also try to be mute or alter his voice so that nobody will recognize him.
 * Jossed. He wears his hoodie and a full face mask.

When Todd finally unmasks himself, it will be a crowd shot
It's the best way to technically say he showed his face, while screwing with his fans. In a review or other TGWTG-affiliated video, Todd will be just an extra with no familiar clothes or features.

The crossover review of Head was imagined/hallucinated by Todd.
At the end of the review, we get a shot of Todd at his piano flanked by Paw and Roses, and they're all singing "Daydream Believer". Fade to black for the credits. Fade back in, it's the same shot but with just Todd. Could just be a coincidence, but the way it's edited seems to imply they were never there to begin with.
 * Todd actually mentions this theory during this review's joint commentary with Paw and Roses, and it meets with their approval.

Todd hides his face out of fear of being killed by a Death Note.
Any other explanations he makes for hiding his identity are lies because if he made it public that he is in danger, he would only put himself at a grater risk. Not only does he make a point to hide his face, but he hasn't revealed his full name. As for why he's being targeted, and by who (Kira?), I can't say.
 * He's being targeted by Justin Beiber, who managed to get his hands on a Death Note.
 * It's lucky YouTube usernames don't count, as it would be a bloodbath. Though, if you've ever read YouTube comments, perhaps it would be for the best.
 * Executives from major record labels, who feel Todd is becoming too big a threat. Executives have been known to posses Death Notes before.

Todd is a Dementor.
Because they also wear hood and it's as good as anything else?

You Cannot Grasp the True Form of Todd In The Shadows
Like Judge Fear from Judge Dredd or Black Mage of Eight Bit Theater, seeing Todd's face would drive you mad. That's why he wears masks and hides in the shadows.
 * This may hold credence. In a recent Nostalgia Chick review, the Makeover Fairy took his mask off. While it was The Un Reveal for us, she freaked out looking at it.

Todd in the Shadows is actually this guy.....
http://www.youtube.com/watch?v=xsveiPJcxlE

Todd in the Shadows is Michael Jackson
Hey, it could happen.

"Born This Way" will make Todd in the Shadows go totally batshit insane.
Come on, it's leaps and bounds more surreal than any of Gaga's earlier music videos. He's going to see it, and it can't be good for him...
 * I'm going with Friday instead.
 * Subverted, at least with "Born This Way". He's perfectly fine. "Judas", on the other hand.

Todd is a SMeyerpire.
He hides his face because his disco-ball skin would immediately reveal him as a vampire and attract an unfathomable amount of flamers

Todd is DJ Axis
He uses the hoodie to not let Handsome Tom notice that he is half-blind (apparently Tom has tried contacting DJ Axis to get him to join The Game Heroes) because he wants to try his hands on stuff other than remixing video game music.

Todd is That Aussie Guy in disguise.
If your wondering about the different humour styles, Todd mentioned stealing many of his jokes from friends and family. That's why he wears the hood: to prevent Doug from learning the truth.

Todd is The Mysterious Stranger.
Both don't show their real face and derive pleasure from mocking how horrible human culture is. But instead of painting broad strokes, he's decided to focus specifically on pop music.

Todd is Ruben Valtierra.
A pianist who gets no respect from his peers and frequently has to hide his face. Watch the video for "The Saga Begins" and tell me otherwise.

Todd is Erik.
That explains the hidden face and musical talent.
 * That would also explain his Stalker With a Crush tendencies towards Lupa and the Nostalgia Chick's obsession with him (seeing as she was majorly infatuated with the musical before).

There is nothing special about Todd.
Since nearly everyone is convinced that he's someone important, it is possible that he's actually a nobody under that mask. He's just a well-spoken young man named Todd.
 * Stupidest thing I've ever heard. Next you'll be suggesting Crookshanks is just a cat.

Todd is The Stig.
Well, why the hell not? Both men hide their faces; we've never seen Todd drive, and we've never heard the Stig talk; ergo....

Todd is a convict hiding from the law.
A bit darker, but we already know he's a magnificent stalker. What else could he be up to in his free time??

Todd's got an Omega deal going on under the hoodie.

 * Again, why not?

Todd has Asperger's Syndrome.

 * This troper has a friend with the disorder that sounds almost identical to Todd, voice, facial/mouth expressions (in Nostalgia Chick 's Movie Reviews), reactions to things, etc. It could happen? (And too, If he is One of Us, he'll Joss this one.)
 * Or maybe your friend just has an uncanny resemblance to Todd.
 * Or maybe your friend IS Todd.

Todd is a rogue or undercover Shade

 * He says he once worked for Lord Vyce here. He joined the site shortly after Vyce was first foreshadowed (As a scout maybe?). The reason he hasn't been deactivated is that either Vyce cut the signal to protect him, leaving an extra ace up his sleeve in case he ever comes back, or he cut it himself as a result of enjoying his new job and wanting to distance himself from his old boss.
 * Perhaps he's from one of the universes Vyce invaded, and was hired to help eliminate the Entity. He may even be from Vyce's universe: the reason he cloaks himself is because the cloak itself is designed to keep him alive in our universe. Kind of like

Todd is an Assassin taking a stand against the Templar-run music industry.

 * I mean, he constantly wears a hood!

Todd is the Anti-Spiral or an avatar thereof.

 * Why does he hide his face? Because he's a Humanoid Abomination with no real form; he butchered a random guy and made a skin suit out of him for when he needs to be seen in the light, but the only salvageable parts were the hands and lower face/upper chest, hence why he covers everything else. Why does he review bad pop songs? He wants to expose them to an audience that likely wouldn't hear them at all if it wasn't for him, hence inflicting soul-crushing despair among them. He can move in the space between spaces, he kills himself multiple times but gets better, and his pining for Obscurus Lupa is a Take That Audience, representing the face that Lupa is beloved by people who will never actually be able to even interact with her, much less date her, again making them despair. It's far from airtight, but if he starts ranting about the moon in a later video, be afraid...

Todd is quite possibly Slenderman, Jeff the Killer, or even a combination of the two.

 * Hey, regarding the third option, black and white does make gray, and as far as we know, Todd might have a bleached-white face or even no face at all

Todd is Meguka.
"Every day I'm sufferin'." Being meguka is suffering. He wears the mask to cover how off-model he really is.

Krin is the Anti-Todd
Todd's title-card artist appears in Linkara's Mr T #2, also obscuring her face with a hoodie, her features over-exposed into blank whiteness. Female to Todd's male, light to his dark, visual instead of musical, Krin is his opposite. If they met, they would either make a perfect couple or annihilate each other.

Todd is a Weaver.
Keeps his face covered, wears a hood, works with music? Of course, the Weavers' eyes were always visible, and Todd's never are... but then again, the Weavers have blue sclera.

Todd is of Lefeinish descent.
Just listen to his thoughts as read by the Nostalgia Chick at the end of her What Women Want review. "Lu... pa... lu... pa..."