What happens when the audience has a tendency to forget that the characters aren't being presented with the same information, view, and experience with the genre that the audience has.
In cases of Audience Awareness Advantage, things that are so utterly embedded in the public consciousness that everyone is assumed to know them wind up being applied to the characters as well, since obviously they're people too. Things the viewer takes for granted because they've been presented to them in an obvious way seem like they should be obvious to the character too, even if there's no real reason to think this. In addition, things the audience sees coming plainly because they're genre tropes we've been exposed to all our lives probably aren't quite so obvious to characters that have no clue they're living in a comic book or crime drama or action film. Finally, the viewer is only ever shown those snapshots of the characters' lives which are most relevant to the plot, which means that, just like people in the real world, they might have other worries, activities, or interests occupying their time off-screen.
This can get especially bad with series that have run long enough that even those who have never so much as read a single issue or watched a single episode can be assumed to have a reasonable chance of knowing these things. Probably not helping are a number of comedies and unthoughtful parodies that lampshade this or take it to extremes, which can make the viewer feel like they're in on some joke the characters aren't. Making everyone and their dog aware of every single trope out there almost certainly doesn't help. ... Ahem.
Basically, if someone is saying "Oh come on, he was so obviously the Evil Overlord shapeshifted into a teenager and pretending to be your best friend for ten years all along!", they're indulging in this trope. See Viewer Stock Phrases for more examples of such.
- Superman is probably the ultimate example of this, and has been for decades (since the Silver Age at the least). For instance, a remarkable number of criminals seemed to not only know that Superman was weakened by Kryptonite, but exactly what each color of Kryptonite would do... even if it was that color of Kryptonite's first time showing up. Because everyone knows Superman is hurt by Kryptonite!
- But even more than that is the whole "people don't know Clark Kent is Superman wearing glasses" deal. Again, having gotten blatant enough that even characters in-universe who are in on the secret have mocked others for not getting it. And the number of times "Clark Kent and Superman are never in the same place together!" is used as evidence is almost appalling.
- Supergirl: A large number of people seem to know Supergirl is Superman's cousin rather than his girlfriend, little sister or fangirl. They know she is specifically his cousin and has his same powers and weaknesses, even in realities where they haven't made their relationship public.
- In Juno, the viewers can see that Mark is simply not that enthusiastic about raising a kid and being around Juno made him feel like a "cool rock star". Everything about how Mark and Vanessa's relationship wasn't quite right was already evident from their first scene and the rest of the movie highlights it. So when Mark attempts to kiss Juno and leaves Vanessa when she was going to adopt, Juno was surprised. It was just that she either didn't realize it or chose to ignore it.
- The Dark Knight Rises receives this in the conclusion; when Batman "died" at the conclusion, viewers the world over cried foul that no one in-universe noticed Bruce Wayne died at the same time, ignoring the fact that plenty of people died and disappeared at that time, so by that logic Batman could have been any of them. Then it's revealed he's actually still alive, and the viewers again demanded to know how no one recognized him, believing that the general public in Italy have all memorized the faces of wealthy Americans and spilled the beans. Especially when everyone thought he was dead anyway. For that matter, every Batman medium has to deal with the "how does anyone not know Bruce Wayne is Batman? He's rich and doesn't socialize! It must be him!"
- The Lovely Bones had some fans complaining how no one suspected Harvey as Suzie's murderer - despite his creepy appearance. Suzie's very opening narration says that when the story takes place, child abduction was not a national crisis.
- Shows up in the Star Wars Expanded Universe.
- The plot of The Thrawn Trilogy partly relies on the fact that Darth Vader being Luke and Leia's father is not common knowledge, and in fact most people aren't even 100% sure that he's dead. With pretty much every book written later, on the other hand, the authors fall victim to this trope and act as though everyone in the galaxy has watched the films and knows everything that happened in them.
- This is also the official explanation for how so many people can be skeptical of the Force in the original trilogy era when the Jedi were active a mere fifteen-to-twenty years previous in the prequels. We've seen plenty of examples of Jedi in action, but most people in the Galaxy Far Far Away haven't. Their information about Jedi and the Force, even during the prequels, amounts to stories about some religious cult that they believe are likely exaggerated and easily dismissed.
- How I Met Your Mother brings us an inverted version of this: while viewers of the first version start out wondering who the great love of Ted will be, this is painfully obvious to his audience, his Future Kids, who are suitably bored. (Also: parents and everything connected to them is boring.)
- Watch episodes from the early seasons of Smallville. In the first few minutes, is there a focus on a new character, probably a teen? Then basically the remaining questions are whether he'll ingest kryptonite directly or via plants/tattoo/ etc., what sort of super power he'll sprout as a result, how quickly he'll turn evil and/or mad, how Clark will stop him and whether or not this will spawn a "What is it you aren't telling me" moment from Lex. Thanks to cultural osmosis, even someone who never watched the show could probably predict at least half the plot.
- This will happen with any competitive Reality Television show, particularly those which are not of a creative nature. Viewers tend to be judgmental about players' strategic moves on Survivor, or missing small details during tasks on The Amazing Race, without taking into account that (a) teams don't get all the information we do, and aren't privy to the Confessionals and strategies of the other players, and (b), are working under massive amounts of fatigue and stress while trying to do these tasks, and tasks are not always laid out for them like they are the audience.
- People with autism are more likely to have what psychologists call a "theory of mind deficit" or "mind blindness". The short play The Sally Anne Test by Simon Baron-Cohen (the cousin of a famous comic actor) invokes this as part of a psychological test designed to measure this in viewers who may have a learning disability. First, Sally and Anne are introduced, and the examiner makes sure viewers know their names. Each is carrying a basket. Sally puts a marble in her basket, puts the basket down, and exits. Anne takes the marble out of Sally's basket and puts it in her own basket. Sally returns, and viewers are asked where Sally is about to look for the marble. The viewer passes if he believes that Sally will first look in her own basket. A viewer who believes that Sally will first look in Anne's basket has mind blindness and has fallen victim to this trope. Baron-Cohen originally staged it as a puppet show; Leslie and Frith staged a production with live actors to rule out the objection that children might not attribute theory of mind to dolls.