No, they are not cute. They are not wonderful. They need to die now, and people need to learn the difference between loving their characters and falling in love with their characters.
To show more clearly what I mean, I'll use a character who could so easily have been an Author's Darling, but instead turned out pretty damn good: Steven Brust's Vlad Taltos.
1) An Author's Darling continually does all the "cool" things. This can include saving the world, but it's actually more likely to include things like:
-figuring out the mystery or main puzzle in an extraordinarily clever way.
-humiliating (rather than triumphing over or fighting) his or her enemies.
-being suspected of wrongdoing, and then proven innocent.
-redeeming a character no one else could bring back to the "light."
-going alone to do something dangerous (no matter how suicidally stupid this seems to the reader).
-saying witty comebacks.
You can, if you've read Harry Potter fanfiction, see it in the way a lot of authors characterize Harry Potter and Draco Malfoy. Everything that adds pizazz and flair to the plot has to come from them. The other characters stand around speechless and stunned, or bow their heads and weep when they realize how wrong they've been.
An Author's Darling doesn't have to be the hero, but quite often he's still the center of the story; the author can't bear to leave him out of the spotlight, so she makes him do something that's guaranteed to draw attention back to him. No other characters will be able to match him, no matter how it seems like they should be able to.
Brust's Vlad Taltos could easily have become like this. He's a witch and a sorcerer, one of the best assassins in the world, a crime boss, friends with lords and ladies, witty, and bonded with a telepathic flying lizard. However, he's also part of a human minority among a powerful non-human majority; he works as an assassin partially to get revenge on them. There are other characters in the books who have the same skills he does and are better with them, and who can hold their own against him in banter. His telepathic companion, Loiosh, insults him, belittles him, and doesn't constantly tell him he loves him. It works.
2) Author's Darlings are the author in miniature. I know that bit about putting pieces of yourself in your characters, but I don't think it works well when people try it deliberately. Much better to get an idea for a character and then notice, "Hey, she's as suspicious of people as I am." It's a process that works best subconsciously.
Taking your own experiences, likes and dislikes and knowingly putting them into the character for no good reason produces an Author's Darling, especially if the character doesn't really change during the course of the story. Maybe you broke your ankle once, so you have the character break her ankle. But what value does this add to the story? Often, nothing. The character broke her ankle. So what? It might make the author smile, but it teaches her nothing new, no more than diary-writing does. In fact, (listen to me declaim) the more self-based a character is, the more uninteresting she's likely to be. The author combines the idea that, "Well, it must be of value because it comes from me" with too little self-knowledge to work out how that experience changed her life, or how the like or dislike formed. Those traits don't develop in isolation. They have a context in the author's life and personality- a context that is completely shattered when it's thrown into another person's life. There it sticks out like the broken bone it is.
I'm always baffled when people say things such as, "She likes to study, because she's based on me." What kind of reason is that? Who cares? Readers of a book engage with the imagined character, not the author. If she needs the depth and strength of your own personality, or even knowledge of your own life, to make any sense, then you've created a Darling and she must die now.
Brust admits that he created Vlad Taltos as a wish-fulfillment character; he was liked but not respected, so Vlad is respected but not liked. He also encounters some of the concepts that interest Brust. However, Vlad doesn't perfectly reflect Brust's political beliefs, as a Darling would. Given his background, it would make no sense. Brust also says that while some of Vlad's experiences reflect his own real-life ones, he had no idea at the time he was writing the book that contains them that that was what he was doing. I think the book (Teckla, which is already troublesome enough for a lot of readers of the series) would have been a much poorer story if he had known and chosen to use Vlad as an outlet for those experiences.
Which is another thing, really.
3) Author's Darlings are the author's opportunity to talk back to people. This is another case of not being truly separate from their authors, but one special enough that I thought it deserved its own mention.
I often feel faintly sick when, reading through a fantasy story, I realize that the author is most likely writing about misunderstanding parents because she has them (or imagines she does), or that she's taunting the bullies who tormented her in high school. She doesn't want to actually talk to these people, or perhaps they're in the past, dead or out of contact, and she can't. So she takes the chance to create a character who's her, put her through the same situation, and say, "Nah-nah-nah-boo-boo!"
Any person who opens a fantasy book in good faith, expecting to be entertained and maybe rapt away deserves better than to be the author's therapy. For that matter, the characters deserve better than that. Examine your life, of course, but do it in a diary, with a therapist, with friends, or by means of a tell-all book. Don't create an Author's Darling just to create the triumph you "should" have had, five or ten or twenty years too late.
Vlad Taltos has an extremely shitty life in many parts of his own series. But he doesn't break down and angst about it; nor does he go back and face down everyone to show them how wrong, wrong, wrong they were. He supposedly kills Draegarans to get revenge on the bullies of his childhood, but all his closest friends are Draegaran. The arguments he gets into with his wife Cawti are probably irreconcilable, and he understands that, and goes on. Would that the authors who use Author's Darlings could do the same.
4) Author's Darlings get gratuitous mentions in parts of the story that are not their own. Even fantasy books with multiple narrators, which is most of them, cannot escape this when an Author's Darling is still breathing. People in other parts of the world have dreams about her. Someone will have a "sudden feeling" that she's in trouble, and probably rush to help. Random characters will wonder about her sex life (this is a common fanfiction plot device in cases where a canon character has been transformed into an Author's Darling). Leaders who met her only once and have more important things to think about will ask about her.
Other times, it's more subtle. Other characters notice something minor that's a side-effect of the Darling's main action, and wonder if it could be connected to her. I can see the author smirking. "But only we really know the truth, don't we?"
Stop dragging me into the steam-house with you, author. It's sticky in there, and not just with heat.
In-jokes are one thing. The author doesn't overemphasize the punchline of the joke, and writes it so that people who might not have read all the other books of the series can still enjoy it as part of a good story. But creating a scene with a sudden, jolting reference to this character who has no reason to appear has the effect of an in-text author's note saying, "Hi, Karen!" It's no doubt fun for the author, but she forgets about making it fun for anyone except her and Karen.
Brust includes a lot of in-jokes in the Vlad series- among others, references to Terry Pratchett, Monty Python, and the Grateful Dead. However, he does not rub the reader's face in it. There are no little tales of Vlad hobnobbing with King Arthur. Instead, there's a character asking Vlad, "How would you like it if I turned you into a newt?" Fun if you get it, fun if you don't. Vlad also casually makes references to adventures all the time that Brust hasn't written, but they never last for more than a line. No "mysterious paragraphs" where the author taunts the reader with his character's Darling status. No plots that would depend on your having read all nine books in a particular order to get them.
5) Author's Darlings are so endlessly "fascinating" to their author that they deserve continual description. To adapt a Jurisimprudence law:
1) Somewhere, someone is laughing at your writing.
2) This person is not "jealous."
Long descriptions can easily lead to more of this non-jealous snickering. The author feels that everything connected to her Darling is so wonderful that we must want to hear about it, too! So we get endless sentences about her hair blazing in the light of the setting sun, her eyes being not just green but emerald and malachite and jade and verdant and viridian, and people who have known her for five hundred pages "still being struck by how gracefully she moved."
Your Darling is not a revelation, author. You are in love with her and seeing her through rose-colored glasses. I am skimming past the descriptions and trying to find the place where they start talking again.
This fascination also leads to very special "As you know, Bob..." conversations. I've lost track of how many fantasy scenes I've read that went like this:
"You still cry about your parents sometimes, don't you?" His voice was soft and tender, and he reached out to put a hand beneath her chin and turn her to face him. She let him, and he felt as if her were drowning in the green of her eyes.
"Yes, I do," she whispered, wiping at the tears with a slender, pale hand. Her russet hair rustled delicately as she bowed her head. "And writhe in the blankets, and weep with the nightmares."
"I know." He closed his eyes, unable to bear the sorrow on her face. "And I would give everything to be able to make it better."
"I know." She leaned close and kissed him on the cheek with her full crimson lips, a caressing gesture like a breeze.
They both know. They both know everything. If it's coming late in the story, chances are the reader does, too. It's really boring, and, for me, even more unforgivable than the "As you know, Bob..." conversations that infodump about the world's history or magic. At least those can include interesting information; the problem is piling too much of it on at once. These are just about the Darling. They also are more likely to take place late in the story, and if we've been seeing her cry and have nightmares, and the guy love her, since the beginning, by now it's beyond tiresome.
There's also no excuse for all the "slender, pale hand" and "russet hair rustled delicately" business (beyond the fact that "russet...rustled" sounds atrocious). What do they add? Nothing, but this is a Darling, so the author assumes we're as interested in her as she is.
Brust writes a very tight, spare style from Vlad's first-person POV, and even then, he's a lot more interested in the other characters and in Vlad's memories that haven't been repeated for book after book than he is in reiterating what's gone before. Vlad is very good at solving mysteries, but he doesn't hash them all out in his memory and then discuss them with people who already know what he's talking about; he waits, then tells the appropriate people at the appropriate time. And thus he escapes Darling status.
Having seen enough truly creepy character obsessions in fandom, I have no desire to see more in fantasy fiction.