Luvvies

"Luvvie" is a slang word for actor originating in British theater, from the tendency of stage actors to call each other "love" and "darling" (apparently because when you're going from job to job it's easier than remembering people's names). The people it refers to tend to be posh and classically trained, and it connotes a certain amount of pomposity, effusiveness, sensitivity, and/or sentimentality.

As you might expect from that description, "luvvie" itself is a generally derogatory word, and this trope is double-edged: the existence of people like this in show business is obviously Truth in Television, and some actors will take huge offense at this perception of their profession, inevitably displaying all of the above qualities in the process of denying it. On the other hand, this trope is easy to overdo, especially in conjunction with an unfair portrayal of the whole art of acting as a self-indulgent sham requiring no work—any actor who talks about their job in public at all, no matter with how clear a sense of proportion, stands a chance of being accused of being like this. Actors who possess a sense of humor often invoke or Lampshade this trope about themselves for Self-Deprecation purposes.

Expect to hear Continuity Lock Out nicknames and references, long-winded stories about working with stars from the previous generation, Compliment Fishing, fits of rage and depression over bad reviews, catty remarks about some colleagues and gushing praise for others, obsession with who wins awards (while pretending not to care), and constant soul-searching and navel-gazing. A luvvie trying to function outside the context of work is often a sad sight to see. He may consider himself a a Sad Clown, Blessed with Suck for being so very talented in a world that doesn't understand. He may actually be that talented—or not. Despite having any or all of these traits, these characters are often regarded affectionately—this is usually Write What You Know, and after all, they have to be played by... actors. There are plenty of people in the real world who are massive luvvies and well liked for it.

Compare Shakespearean Actors, Large Ham, Classically-Trained Extra, Wag the Director. A particularly unsympathetic portrayal might make them Nice Character, Mean Actor. They live in the same world as the Prima Donna Director and Caustic Critic. Luvvies are Always Camp, even the women.

Examples of Luvvies include:

Film

Withnail of Withnail and I. Marwood's relatively more adult attitude ends up getting him a job, while Withnail is left performing Hamlet to some captive wolves.
Part of the joke of Shakespeare in Love is assuming that actors 400 years ago were already like this.

Ned: [about Christopher Marlowe's death] Marlowe attacked and got his own knife in the eye. An quarrel about the bill.
Fennyman: The bill? Oh, vanity, vanity!
Ned: Not the billing. The bill.

Literature

I, An Actor: Another Great Actor Exposes Himself by "Nicholas Craig" (see below).
In The Man In The Rubber Mask, Robert Llewellyn's autobiography, he keeps track of his own luvviness, at one point comparing himself to the aforementioned Nicholas Craig.

Live Action Television

Extras naturally featured this a little bit.
In early seasons, QI used to have a "Luvvie Alarm" they would set off when a panellist was judged to have crossed into this territory while telling a story. Stephen Fry and John Sessions were both guilty. In the "Films & Fame" episode (for the sake of which it was a good thing they'd retired the alarm a long time before, or else Sessions would have singlehandedly caused a power outage in the studio), we got this exchange:

Emma Thompson: You know the word "luvvie"?
Stephen: Yeah?
Emma: What do you all feel about it?
Stephen: [sigh] I mean, I'm not going to get as upset as some actors do -- some actors say, "We do a bloody hard job of work, we're serious people, you know, it's a coal face, doing a play! How dare they call us luvvies!" I think that's a bit overdone. On the other hand, it's a bit tedious when the Daily Mail says "luvvie couple XYZ," or something....
Emma: Do you know what the first citation of it is in the OED?
Stephen: No.
Emma: It's you.
[cue My God, What Have I Done? reaction from Stephen]

Both parties in the above example were in the Cambridge Footlights together, and each had a sketch in their revue where they played this type of character (him as a host of an acting masterclass show dispensing idiotic "wisdom" to a student played by Hugh Laurie, her as an actress obnoxiously receiving an award).
Later, in A Bit of Fry and Laurie, there was a sketch where Laurie was a luvvie claiming he used to know "absolutely everyone" in the business, and Fry was an interviewer who got annoyed and started asking about various made-up people with Unfortunate Names ("Fenella Hahahahahaha!spuit?"). Laurie kept pretending he recognized them, until the punchline: "Dick Van Dyke?" "You just made that up!"
Inside the Actors Studio is often accused of this—comedian David Cross hates it, and has a long routine making fun of the way James Lipton fawns over guests whether they've done anything to deserve it or not.
The Nigel Planer character Nicholas Craig, star of Nicholas Craig -- The Naked Actor and The Nicholas Craig Masterclass.

Magazines

Private Eye has a feature called "Luvvies" specifically for quotes from actors that exemplify this trope.

Newspaper Comics

Alex: In one strip, Alex and Clive are in a bar discussing Quentin Tarantino's plan to make a Shakespeare movie. Clive makes a joke "I can see it now: Quentin Tarantino's 'F*@# Macbeth'." One of the pther patrons objects to Clive's language and he immediately apologises and corrects himself to 'F*@# The Scottish Play' as the final panel reveals the bar is full of luvvies.