Angel: Career week?
Buffy: How did you know?
Angel: I lurk.
...and the shot pans out to reveal a mysterious character, concealing his eyes behind mysterious shades and covering his face with a mysterious shadow, watching. Just... watching. Clearly, he's been there for a while. Observing the hero fighting. Assessing. Judging. And he's probably standing on top of a lamp-post while doing it.
Likely, the next episode will be all about him, revealing whether he's working alone or as part of the Ancient Conspiracy, whether he'll be The Rival, the Worthy Opponent, or the guy who's always just passing through when you need help, and probably - through the new character - expand the scope and size of The 'Verse.
Sometimes, a particularly mysterious stranger will watch the heroes for several episodes. Bonus points if he's seen noting something down on a PDA or notepad, or radioing information to The Omniscient Council of Vagueness through an earpiece or walkie-talkie. These days, some of them even use cellphones.
Mysterious Stranger is the supertrope. Mysterious Protector is a particular subtype of this - specifically, a 'benevolent' version. This guy just as often turns out to be a foil, rival, or downright antagonist. This trope is sometimes also combined with Chekhov's Gunman. The Mysterious Employer is another subtype: instead of being "benevolent" per se, they direct the heroes in some way.
Not to be confused with The Watcher, whose explicitly-stated role is to observe events from afar (and whose implicit role is to pop in to offer advice to the protagonists).
- In Cardcaptor Sakura, both Shaoran Li and Kaho Mizuki are introduced this way. Kaho is particularly noticeable for wearing shades during her enigmatic first appearance, and never again.
- Bakura in the Yu-Gi-Oh! anime spent some time lurking in the background before he actually started playing a role.
- Madoka, Arisu, Kaede and Sai in Kidou Tenshi Angelic Layer. In the manga, they were even shown in silhouette. The English VAs for Tamayo and Koutarou lampshade the practice in an audio commentary, complaining that "soon, they'll have more lines than we do". Shuuko later takes up this role.
- Caren in Mermaid Melody Pichi Pichi Pitch. Later, Sara indulges in it once in a while.
- During the Makoto arc of Kanon, Amano Mishio stalks Makoto and Yuuichi before making herself known.
- The invisible presence of Hanyuu in early chapters of Higurashi: When They Cry is a tragic version of this, seeing how much of events is driven by misunderstanding and paranoia.
- Frederica Bernkastel may also count, seeing as she writes poems about the series' events without actually interfering.
- This is how it was confirmed that Johan was still alive on Yu-Gi-Oh! GX. Edo also liked doing this while he was playing Batman.
- Slayers NEXT introduced Xellos as a shady, albeit cheerful, tag-along character whose job was to observe Lina to assess her abilities, on behalf of the Mozoku race. The reason being, he was to try to persuade her to join their clan, if he determined her power could be of use to them. Of course, if she refused, or if she was perceived to be a possible threat to them, Xellos' orders would be to kill her on the spot.
- Autor in Princess Tutu is usually just a Chekhov's Gunman that "just happens" to be in the library the same time as Fakir, but in two episodes he's shown just...watching Fakir. His eyes are covered up by Scary Shiny Glasses until the episode that he gets a line outside of "Will you please be quiet?!"
- Col. Mike Franklin from Transformers Cybertron. He has an interest in the Transformers because one saved him from drowning when he was a kid, and at the halfway point he becomes an ally of the Autobots.
- The ninja, Toyata, in Y: The Last Man. For a long time her whole schtick was just watching the heroes through binoculars. Then her schtick became screwing over the heroes. Her first appearance was kind of both, though.
- The Clone Saga of Spider-Man has a wild number of different Mysterious Watchers, to the point where even The Life of Reilly mentions it.
- In DC Comics's different titles in the months leading up to the Crisis on Infinite Earths, the Monitor was depicted this way. He was not clearly seen, and he was "monitoring" the activities of different super-powered beings, sometimes intervening in various roundabout ways to put them in jeopardy to "test" them. He was made to look very sinister. Then the actual Crisis happened and he turned out to be the Big Good.
- Star Wars: Legacy handled Azlyn Rae's introduction that way.
- Capes featured a shady young man constantly spying on Bolt and muttering about getting revenge for his father. "Soon, Bolt... soon." When he meets a nice girl while stalking his prey and gets engaged to her not long after, he amends his mission statement to "...Later, Bolt. Later." Who he is and what Bolt did to his father are never explained.
- Tim Drake was first introduced as a mysterious figure only shown from the back who stepped out of the shadows after Batman stumbled away injured to the Batmobile at the end of an issue to reveal he'd been following Batman, knew he was Bruce Wayne and was taking pictures of his fights.
- Burning Black has one show up at the end of Act 4. Whoever or whatever it is, it implies that it's been secretly aiding Timmy for some time, and seems to have it's own vendetta against Remy and the Pixies.
- The Pony POV Series has the Interviewers. Originally just a plot device, they've since evolved to something much more integral to the story, not least of all because they know much more than they should, including things they couldn't know.
- Friendship is Magic: The Adventures of Spike: Two of them, viewing Spike remotely, are introduced in the Spike of Saddle Arabia arc. And judging by their comments, they're on the malevolent side of things.
- The eleventh story of the Facing the Future Series introduces one who goes by the name "G". He seems to be working for some organization that has ordered him to keep an eye on Danny. Fortunately, he seems to be an ally.
- In The King's Justice, Kelson sends Conall and an escort to conduct Princess Janniver and the nuns of a convent sacked by Mearan rebels to safety in Rhemuth, then expresses his wish to leave in pursuit of the rebel forces. "As Morgan gave the orders and the officers scattered to relay them, neither king nor general noticed a R'Kassan scout draw apart from his fellows and disappear beyond the picket lines, obscured by the bustle of breaking camp." He is later revealed to be an agent of Princess Sofiana's, who shares what she has learned from him with the rest of the Camberian Council.
- The Dread Pirate Roberts, in the original novel of The Princess Bride, is doing exactly this in his first appearance in the story.
- The Dinosaur Lords has the Witness, who has taken a strange liking to Karyl and is observing him and Shiraa whenever something big is about to happen. She's the spirit of Paradise and is sizing Karyl up to be her Champion.
- This is how Angel first appeared on Buffy the Vampire Slayer, despite not being Buffy's actual Watcher. In fact, when she later meets her Watcher, Giles, she wrongly assumes that Angel is affiliated with him.
- Spike sometimes tries to do this, but has a tendency to get bored and try the Indy Ploy instead.
- Ruby on Supernatural spent some time mysteriously stalking Sam before revealing herself.
- At the end of the season 5 finale, after Sam is sucked into hell and Dean has gone to live with Lisa & Ben, we see a shot from outside the house: Sam is watching them eat dinner.
- Sela on Star Trek: The Next Generation.
- The Watchers from Highlander: The Series.
- In The X-Files, the Cigarette Smoking Man spent much of Season One standing in the background looking mysterious and occasionally filing away some vital piece of evidence that had gone missing from the crime scene.
- At the end of the second series of Robin of Sherwood, after Robin has been killed, the outlaws see a hooded figure who looks like Robin (and at this point is presumably still played by Michael Praed). At the beginning of Series 3 he is revealed to be Robert of Huntingdon (Jason Connery), who becomes the new Robin.
- Dwight Dixon in Pushing Daisies has a tendency to lurk in the background, watching, plotting, usually carrying some sort of firearm...
- After Dwight Dixon dies, the episode The Norweignians sets up another Mysterious Watcher... Ned's father, who abandoned his son as a child. Cue cancellation.
- The Observer (AKA September) from Fringe appears in every episode, sometimes only for a few seconds and usually without the characters noticing. The episode that revealed him was a subversion of this trope as he got punched in the face for his trouble. He and his fellow Observers are a group of men with advanced technology who observe key events in history for unknown reasons, but are bound to not interfere.
- HRG, from Heroes. He later becomes a central character after he's revealed as Claire's father, but for the length of the pilot all we saw was a mysterious guy in horn-rimmed glasses.
- Tower Prep features one in its pilot.
- The aptly-named Watcher (now using the pseudonym
WillJoshua) from No Ordinary Family.
- In Teen Wolf, Derek fulfills this role to a T, complete with a Stealth Hi/Bye almost every single time he appears.
- Person of Interest actually has its two main protagonists embody the trope. The Government has a secret system, a machine that spies on you every hour of every day. Michael Emerson knows because he built it.
- Doctor Who: Throughout "Logopolis", the Doctor keeps catching sight of a mysterious white figure who is observing him. The Watcher (as he is called out in the credits) turns out to be a presaging of the Doctor's forthcoming regeneration, who merges with the Doctor when he regenerates.
- Peter Schilling's "Error In The System" has this line:
"Somewhere a computer records us from afar, looking for the error in the system on this star."
- Gamov from the Xbox remake of Ninja Gaiden, complete with coat, shades and high vantage point. He does introduce himself to Ryu quite early, but otherwise spends his time as one of these characters is meant to act.
- Raven from Tekken 5 is introduced as one of these in the opening animation. And he's still one by the end of the game, because even if you play as him you never find out who he's actually working for.
- The G-Man from Half-Life is a textbook case. He even manages to keep up the schtick after meeting the hero face-to-face, since even then he says a lot but reveals exactly squat.
- The Stranger from The Walking Dead was first referred to as "The Voice on the Radio" because all that was known about him was that he was watching you and every now and then would send a vague message through a walkie-talkie. When he is finally met, he's merely a Hero of Another Story whose life was ruined by the heroes of your story.
- Throughout the FEAR games, there will be moments where, if you're quick enough, you can spot some thing watching you from corners or the ceilings of rooms, before sprinting off in a barely-visible blur and disappearing into an air vent or behind a grating. Sometimes, these are just the Replica Assassins that have been quietly tailing you throughout the game and feeding your location to their comrades. Other times, they're something worse....
- King comments on events in Third Super Robot Wars Z: Jigoku-hen with Queen. He holds a meeting with Cygus when he joins Chrono.
- Batman: Arkham City has a mysterious hooded man who appears watching Batman at certain points in the game. Approaching him causes him to say something vague and vanish, leaving a strange symbol behind. Finding him enough times reveals that he is recurring Batman character Azrael, and he has come to warn Batman of the events of Batman: Arkham Knight.
- In the Lonesome Road DLC of Fallout: New Vegas, Ulysses can occasionally be spotted in certain parts far from your current location, observing you G-Man style.
- In Sly Cooper: Thieves in Time, Clockwerk, the Big Bad of the first game can occasionally be seen in the background of the various stages, which is consistent with his reputation of observing the Coopers throughout history.
- The TicTocs (also called the thousand eyes) from Gunnerkrigg Court have been watching since the very first chapter. We still don't know who they work for, or what their goals are.
- The Mysterious Watchful Presence watches mysteriously at the end of Chapter 1 of Everyday Heroes.
- Vampire Cheerleaders: The mothmen have kept tabs on each of the PMS crew's adventures, since the beginning and seem to have a keen interest in Charlotte and Stephanie. After silently observing them for months, they eventually abduct Stephanie and appoint her as their new Queen.
- "Lurking" is a term on the internet that refers to observing social websites that encourage contribution and nothing else—just observing. In fact, in some circles it is encouraged before one should actually participate in order to glean more about the community's culture and various rules. You're probably doing it right now.
- The Watchers in lonelygirl15 and KateModern. Subverted in lonelygirl15 series 3: after the death of Bill Porter, his Shadow starts following the gang, appearing in the background of several videos, and leaving threatening messages. He then runs out into the road and gets run over, ending that plotline abruptly.
- The Slender Man Mythos: The Slender Man tends to do this. And then he gets a bit more up close and personal. A lot of Slender Man series have a proxy-type character who makes contact with the protagonist through written messages or video updates; their nature and relationship to tall dark and Slender varies depending on the series. The two most famous would have to be totheark from Marble Hornets, and the Observer from Tribe Twelve.
- There was an episode of Batman: The Animated Series where, after teaming up with a Femme Fatale to fight a supervillain, the episode ended with Ra's Al'Ghul watching from afar via a Palantir Ploy, and saying something like "Most impressive, Detective" - and then later becoming the enemy in a two-parter. It's not Batman's fault that we all know Ra from his appearances in all the other series, movies, and comic-books. To be fair, this was the first appearance of Ra's outside the comics, and most non-comics fans don't know who he is, even after Batman Begins.