Informed Difference: A work claims that the monsters are not the monsters they resemble or that human beliefs are wrong about their nature, but the monsters turn out to be functionality similar if not the same as their traditional portrayals. The argument that the monsters are different is moot.
Indirect Difference: A work goes out of its way to claim that the monsters are different from their traditional portrayal - and yet, the monsters as presented follow tradition to a tee... while usually lacking its justification. This typically occurs because of a change to an important tangential issue that should affect the monsters but doesn't.
Demons But No Heaven: If classicaldemons are featured in settings absent of God and/or Satan or analogues thereof, the question of "why?" is raised. Older traditions have the nature of one side in the Heaven-Hell conflict shaping the image of the other, but if there is no Heaven with armies of angels or if those heavenly forces are Knight Templar types or otherwise Light Is Not Good, then how did the demons become evil?
Incongruous Atavism: The monsters are changed from the traditional portrayal in some way, while retaining other aspects that make no sense with regard to the change simply because it is traditional. This problem is almost never justified or even lampshaded.
Contagious Vampire/Werewolf Species: If vampires (or werewolves and other lycanthropes) are portrayed as a species instead of a curse or disease, they may still possess the ability to change humans into pseudo-vampires (that themselves may or may not be able to change other humans in turn). As the vampires can already reproduce sexually and transforming humans willy-nilly just creates competition for food, it brings up the question why the original vampires would have developed this ability other than tradition.
In Devilman and related series, God was an alien, and the demons were upset at being rejected. Yet, (save the hero and his fellow hybrids) they are never shown to be anything but monsters eating people and wiping them away in the most gruesome, often taunting manner imaginable.
Lampshaded in Vampire Knight. Yuki has known about vampires since she was a child and since her vampires are their own race, she believes that the idea of a human being changed into a vampire through bite is a silly superstition until her adopted brother Zero, the sole survivor of a vampire attack that killed his family, sinks his fangs into her neck.
Inverted in The Record Of A Fallen Vampire. Their vampires and dhampirs are styled in the traditional manner (high collared capes, bat wings, fangs, etc) but do not consume human blood, a signature identifying trait of vampires in fiction. This is justified by stating that the primordial ancestors of all currently living vampires did consume human blood, but their modern descendants have long since evolved out of this trait.
John Carpenter's Prince of Darkness has the order of the evil hierarchy feature a nasty surprise twist, and Jesus is a time-traveler/alien offering warnings to people in a past era who were woefully unprepared to transmit his warning. The Church is revealed to be a very ineffective secret-keeper. Yet the fate of the world should the Uber Big Bad prevail seems to be a very traditional one.
In Werewolf, the resident Mr. Exposition identifies the bones from an archeological dig as a Navajo skin-walker, and he spells out exactly how those differed from the traditional Hollywood wolf-man. But anyone who gets cut by that skeleton's teeth turns into a werewolf, and looks more or less exactly like the traditional Hollywood wolf-man.
Christopher Brookmyre's Pandaemonium, in which a group of (admittedly badass) Scottish schoolpupils have to fight off an incursion from a different dimension. What the Roman Catholic Church presumes to be, and perversely wants to be, demons from Hell turn out in the end to be nothing of the sort, even though they look the part, right down to the horns and cloven hooves.
The Buffyverse originally introduced "demons" as the series' Monster of the Week, though the mythology was very Lowest Cosmic Denominator. Originally demons were just random monsters (only a very small number of which were a Big Red Devil), but as the series went on it was revealed that some demons were actually fairly decent people aside from being unusual. This didn't change the fact that most of the demons in series were still random monsters, and raises the question of why the word "demon" is used in the first place since in this context it carries the same weight as "space alien."
In Dungeons & Dragons, lycanthropes are a race of their own that carry a disease that causes other races to develop lycanthropic characteristics without actually becoming true lycanthropes; the "natural" lycanthropes breed true, but "infected" lycanthropes do not. This is justified in the sourcebook Van Richten's Guide to Lycanthropes in which scientifically-inclined monster hunter Van Richten speculates on a logical progression where, in the distant past, the original infected lycanthropes might have developed a symbiosis with the disease and mutated into natural lycanthropes. This logic makes less sense in later editions of the game, where infected lycanthropes cannot pass on the disease and the "weretouched" (aka shifters) were introduced as the watered-down descendants of lycanthropes who interbred with non-lycanthropes.
In Runescape, Lowerniel Drakan (the vampire leader) comes from another realm called Vampyrium, and possibly some of the ranking Vyre Lords do as well. Most, however, are humans who were converted via unknown means. Since the "cattle" who live in Meyerditch's ghettos get bitten all the time when they have to give tithes, a mere bite will not turn a human. Also, in the first novel, a werewolf is interrogating someone and assures him after biting him that humans cannot be turned by any means.
Lucy, the Daughter of the Devil has an episode centering around the Special Fathers fighting an invasion of altar boy and choir boy vampires who have been praying preying on Catholic priests. They meet up with a guy who is supposed to get them reacquainted with vampire hunting, with amusing results:
Nightshade: As I'm sure the Special Fathers will tell you, hunting vampires... well, forget everything you've seen in the movies. It's all bunk.
Sister Mary: Sunlight?
Nightshade: Oh, no, actually, OK. Sunlight is real. Sunlight can kill a vampire.
Sister Mary: Stake in the heart?
Nightshade: Y-yeah, hold on, let me give you my spiel, okay?
Sister Mary: Sorry.
Nightshade: Forget what you've seen in the movies. It's all bunk.
Father Cantalupi: You know, Nightshade, I've heard that line in the movies.
Five hats means that five tropers think it is ready to publish.
You are saying that you think this draft is ready to be published. That means the description is not ambiguous,
it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.
Is that what you meant to do?
You are saying this draft has a ready-to-publish hat it does not deserve and you are taking it back.