Anti-Climactic Unmasking

""What did you expect? A Monster?"

- Machine, 8mm

"Harley Quinn: (Re: the captured Batman) Ain't you gonna take his mask off and find out who he is? The Joker: And reduce my primal enemy to a mere man? Harley, dear, I'm so disappointed in you! Where's the fun in that?"

- Batman the Brave And The Bold

The Hero's been captured by his Arch Nemesis, who is fed up with all his meddling and wants to dispose of him once and for all. But first, the villain is curious to find out just who exactly has been plaguing him and disrupting his schemes for all this time. Who is behind that mask? With eager glee, the villain takes off the hero's mask and reveals...

...an average, completely unremarkable joe.

Well, that was completely pointless. It turns out that, in addition to his mask, The Hero has something much more powerful protecting his Secret Identity: obscurity. The guy under that super suit could be the same guy bagging your groceries at Walmart. He could be your kid's soccer coach. He could be the President's niece's boyfriend. He's just one of a billion average faces amongst the entire human race.

Please note, however, that this doesn't mean that the mask is useless. All it would take is enough people getting a good look at his face (such as in print, on television, or—worse yet—on the internet) and the hero's identity is blown for good. The mask helps keep the face beneath it obscure enough to keep him Hidden in Plain Sight.

Do not confuse with They Look Just Like Everyone Else, when the villain has no alter ego and is simply too plain to distinguish from ordinary people, or The Un-Reveal, when taking away one mask simply reveals another. This can overlap with Stranger Behind the Mask, if the audience has never seen the unmasked party before. But this trope, emphasizes that it's a stranger to the in-universe characters.

Anime and Manga

 * In the second season of Jubei-chan, Mikage pulls off the face mask on the mysterious antagonistic swordswoman who is threatening Jiyu. ....nothing. It means nothing; because Freesia ages up when she transforms; and her older face isn't similar enough to her child face.

Comics

 * In one Spider-Man comic, the Vulture finally manages to unmask Spider-Man after years of their cat and mouse games and is dismayed to realize that his archenemy could be just some guy pumping gas for a living. "You could be anybody . . ." he says, disheartened. It didn't help that, at the time, Spidey had been hit with an age-accelerating machine so not only did the Vulture see a man he did not recognize, the man was 70 + years old when normally, he was much younger.
 * An early issue of Ultimate Spider-Man had Peter get unmasked by the Kingpin and his thugs, but not know who he was.
 * Steve Ditko did this even earlier in Spider-Man with Electro's first appearance. Spidey defeats him, and unmasks Electro but sees a stranger and remarks that he shouldn't have been surprised that the new villain turned out to be just some guy he'd never met.
 * A relatively common reaction from villains who manage to see Spidey's face is to lament how average or unimpressive-looking he is.
 * This is Older Than They Think, since this situation first occurred in a Golden Age Green Lantern story. The thugs didn't recognize an unmasked Alan Scott, since he wasn't anybody particularly prominent, but.
 * Deconstructed (like many other things) in Watchmen.
 * In Empowered, when some villains unmask the eponymous heroine and are surprised not to recognize her, she stalls for time by trying to convince everyone that she's really a cross-dressing man (despite her ultra-skin-tight costume), and so are all the other members of her super-team. This works, and she's rescued, but the story turns up on the news the next day.
 * In Astonishing X-Men as written by Warren Ellis, the X-Men spend the better part of a story arc hunting down a man named Kaga who is using dead X-Men, Brood and Sentinels to try and kill them. Kaga turns out to be  Even better, his motivation for trying to kill them is anticlimatic in itself, amounting to   Kaga himself lampshades this, sneering "What were you expecting? A master plan? A scheme to turn off the sun? This is the real world. Hatred and disgust are good enough reasons to want to kill people."
 * The long-running Scourge of the Underworld storyline in the Marvel Universe ended when Captain America (comics) caught and unmasked Scourge, only to discover that he was no one we'd ever seen before, and claimed to be the previously unmentioned brother of one of the villains killed by Scourge.

Film

 * In Spider Man 2, Spider-Man's mask is removed after he saves a train full of innocent civilians. They take a glance at him and realize that he could be anyone. One guy even states that Peter Parker looks a lot like his own son.
 * Played with in the 2009 Speed Racer movie. Right after the Monte Cristo 5000 race, Speed and Racer X meet on an empty track. When Speed claims that X is his older brother, X removes his mask to show that he is just some guy—not Speed's older brother, Rex Racer. This turns out to be a ruse pulled off thanks to Magic Plastic Surgery, because as we all know,.
 * Quietly played straight in Kick-Ass. Our hero is beaten down by thugs early into the film and stripped of his costume by the paramedics. They toss the suit out and never tell his father. Later, when Kick-Ass becomes all the rage, it seems no one remembers that geeky kid who was just one more random mugging victim.
 * Inverted and combined with Stranger Behind the Mask during the ending to 8mm when Nicolas Cage takes the mask off Machine and he's just a bald fat guy who "does it because he enjoys it". He even has a speech about the fact his unmasking was inevitably going to be anti-climactic.

Theatre

 * Played with in The Mystery of Irma Vep. Since all the characters are played by only two actors, when is unmasked, for a moment, the other character thinks it's actually.

Video Games

 * Much like the page quote above, The Joker defies this trope in Batman: Arkham City when Harley Quinn tries to remove Batman's mask.

Western Animation

 * In the Justice League cartoon, Lex Luthor has swapped bodies with The Flash. As he's being chased through the Watchtower by the rest of the League, he stops in a bathroom and muses that at the very least, he has the opportunity to learn Flash's secret identity. He looks in the mirror and takes off his mask, looks annoyed for a moment, then comments that he has no idea who the heck he is.
 * In Spider-Man the Animated Series, Peter is suffering from Power Incontinence and is facing off against the Insidious Six. Because he lacks his powers and is facing off against six super-powered foes, he is quickly beaten and unmasked before Kingpin and dissatisfied members of his criminal empire like Silvermane... only for Doctor Octopus to declare that Peter Parker could not be Spider-Man (due to his seeming lack of powers). This pisses off Silvermane and he mocks Kingpin for supposedly kidnapping an old woman and forcing her desperate nephew to play along.
 * In Batman the Animated Series Batman's unmasking of Bane reveals, not Venom-twisted monstrosity, but simply vaguely handsome, boyish face with nothing really remarkable about it.
 * Defied in Batman the Brave And The Bold (see page quote)--The Joker doesn't want to unmask Batman because it's Batman he's obsessed with. Finding the person under the hood would just ruin the fun.