When Nichelle Nichols, the African-American actress who played Lt. Uhura, decided to quit the television show after its first season in 1966, she just happened to meet a beaming Trekkie who told her he loved "Star Trek."

It was the Rev. Martin Luther King Jr.

King approached Nichols at a Beverly Hills fund-raiser and told her "Star Trek" was the only show he let his children stay up late to watch. His smile evaporated though when Nichols broke the news. He told her she couldn't leave because the world was finally seeing blacks on television, not as servants but as beautiful, intelligent people journeying to the stars.

"At that moment, the world tilted for me," Nichols said as she told the story for a documentary on TV's greatest pioneers. "That's all I could think of, everything that Dr. King said -- 'The world would see us for the first time as we should be seen.' "

If King clicked on TV today, he might shout that we've reached the Promised Land. A racial revolution is quietly taking place on the small screen, and zombies, witches and headless horsemen are leading the way. There's been an explosion of multiracial casting on science-fiction, fantasy and horror shows, and the people powering this trend say it is here to stay.

Popular shows such as "The Walking Dead," "Sleepy Hollow" and "Arrow" are giving us a sneak preview of a post-racial America that can still seem far away, fans and creators say. The most eye-popping elements are not the special effects and supernatural creatures but the multiracial casts and the casual acceptance of racial differences. These shows routinely feature actors of color in nonstereotypical roles, and interracial relationships are the norm.

Frankenstein meets the X-Men

In our real world, racial tensions erupt over everything from "stand-your-ground" gun laws to a white rock musician calling the nation's first black president a "subhuman mongrel." But in the world of sci-fi, fantasy and horror, storytellers can ignore reality and create an alternative America where anyone, regardless of race or gender, can be a superhero.

AMC's "The Walking Dead" shows a world where even the zombies come from all sorts of racial backgrounds.

"Sometimes you have to show people the world you want them to see before they can believe it's possible," says K. Tempest Bradford, a sci-fi author and member of the Carl Brandon Society , a nonprofit group that raises awareness of people of color in the sci-fi, horror and fantasy fields.

This mini-racial awakening on TV is new, but its roots are more than two centuries old. The persecuted outsider has long been a central character in classic sci-fi, fantasy and horror tales. When Mary Shelley's "Frankenstein" was published in 1818, it featured a character who was treated like a monster because of his appearance. The popular X-Men comic books, which depict "mutant" superheroes as an embattled minority, debuted in 1963 at the height of the civil rights movement.

"When you look at any kind of monster, they are sort of 'the other,' '' says Gale Anne Hurd, executive producer of the AMC hit show "The Walking Dead," which depicts a multiracial cast of survivors fighting zombies in a post-apocalyptic United States.

"They've always challenged our assumption that someone who doesn't look like us is someone to be feared, and that often the person who looks like us is the monster who should be feared."

Traditionally these classic stories of persecuted minorities have been told by white men such as "Star Trek" creator Gene Roddenberry and Stan Lee, the visionary behind Marvel Comics' franchises such as "Spider-Man." Now a new generation of writers and actors on TV are flipping that script. They explain why there's been a racial awakening, why it matters, and cite the shows that best illustrate this trend.

Hollywood's rejection of a screen legend

Before there was any kind of racial awakening on TV though, Hollywood was a brutal place for actors of color. One famous story shows why.

In 1971, the producers of a new television series were looking for someone to play a Chinese Kung Fu master roaming the 19th-century American West. They considered an unknown Chinese actor but eventually chose American David Carradine. He didn't know any martial arts but apparently the producers didn't think television audiences were ready for a Chinese action star.

The jilted Chinese actor left Hollywood in frustration and traveled to Hong Kong, where he starred in three martial arts films. His name was Bruce Lee.

"Sleepy Hollow" breaks ground with two African-American actresses in leads. Nicole Beharie stars with Tom Mison.

Lee's inability to get the lead role in the TV series that became known as "Kung Fu" is a well-known story. There's been a long debate over the specifics of his involvement with "Kung Fu." Still, the only consistent role Lee could get in Hollywood during the late 1960s was playing the chauffeur Kato in a short-lived series called "The Green Hornet."

To see how much television has changed, one should look at an engrossing, contemporary fantasy show that bears many similarities to "The Green Hornet."

The show is called "Arrow," and while there are Asian actors, none plays a chauffeur. Like the Green Hornet, the lead character of the CW Network show is a wealthy young man who becomes a masked vigilante at night to battle crime. He also has a chauffeur who acts as his bodyguard and confidant. The hero even wears a green mask.

But that's where the similarities end. The cast of "Arrow" looks like a miniature United Nations: Asian actors play complex characters and love interests; the show's villain is played by a Latino actor; black and biracial characters are common; and two interracial relationships are central to the show.

A TV show that's trying to say something about America should look like America, says "Arrow" creator Marc Guggenheim.

"You're trying to hold a mirror up to society, and if that mirror is skewed in one direction, then it's not a true mirror," Guggenheim says.

Ask Guggenheim and other creators of these sci-fi, fantasy and horror shows to elaborate, and they say the same things: We try to reflect the world we live in; we grew up with friends from different races so we don't like all-white backdrops; successful shows such as "Grey's Anatomy" and "Scandal" prove that all of TV is getting more diverse.

Making dollars, making sense

Diversity also makes dollars and sense -- it's good for ratings and the bottom line, the creators say. A recent study backs them up.

TV shows that hire more racially diverse casts and writing staffs attract more viewers, a 2012 UCLA study found . Cable shows with 30% to 40% minority casts brought in bigger audiences; shows with casts and writing staffs that were less than 10% minority had the lowest ratings, researchers at the Ralph J. Bunche Center for African American Studies at UCLA concluded.

At some point you start to normalize the notion that only white men can be the hero and only white men can be in charge. UCLA professor Darnell Hunt on stories that only show white men saving the world

Despite these numbers, minorities, who collectively accounted for 36.3% of the U.S. population in 2010, are still under-represented on television, the study said. Minority actors claimed 5.1% of the lead roles in comedies and dramas on broadcast TV and 14.7% on cable TV, which is traditionally more daring.

"America has gotten a lot more diverse, but Hollywood is not keeping up," says Darnell Hunt, a UCLA sociology professor and director of the Bunche Center.

Hunt says it appears that sci-fi, fantasy and horror TV shows employ more actors of color, but his study didn't look at those specific genres. But he says "there's something" to the trend and it might be due to the urban settings for shows such as "The Walking Dead."

"You're dealing with ensemble shows with relatively large casts set in urban settings," he says. "There's some recognition from the people who make these shows that we have to be a lot more diverse."

There's also recognition from actors of color that a more diverse audience won't accept them in stereotypical roles, says Russell Hornsby, co-star of the NBC series "Grimm," a police procedural that features a homicide detective hunting supernatural characters inspired by the Brothers Grimm's fairy tales.

Actors of color wouldn't complain before about being cast in stereotypical roles in shows such as the 1996 series "Homeboys in Outer Space," says Hornsby, who plays detective Hank Griffin in "Grimm."

"The excuse we gave is that we were just happy to be in the game," Hornsby says. "Twenty years ago that was fine, but not any longer. We're savvier as a people. We're asking for our characters of color to be well-drawn."

The impact of Octavia Butler

So are television fans.

In the 1960s, when "Star Trek" became one of the first shows to field a racially diverse cast, television audiences couldn't easily reach a writer or producer to tell them they didn't like how a character was being portrayed.

Shows such as the 1960s sci-fi TV series "Lost in Space" were set in the future, which appeared to be all-white.

Today, fans don't have that problem -- they can act as virtual co-creators of shows. They hop onto social media sites such as Facebook, Tumblr and Reddit and launch online campaigns to shape casting choices, alter storylines and complain if they don't think a cast is diverse, says Tara Aquino, pop culture editor at Complex. Aquino, who is Filipino-American, recently wrote an online column condemning makers of the CBS series "How I Met Your Mother" for showing characters in yellow face dressed in kimonos. She's a big fan of "Arrow."

"It's important that these characters are not sidekicks anymore or characters to fill a quota," Aquino says.

There's also something inherent in nerd culture that makes sci-fi, fantasy and horror fans more demanding of tolerance, others say. Many self-described geeks never quite fit in and have more sympathy for outcasts because they identify with being victims of prejudice.

Perhaps the most unheralded change in the sci-fi and fantasy worlds is the color of the storytellers themselves. Minority writers have traditionally been expected to write angry tomes about the suffering of their people. But not all black writers, for example, wanted to write another "Roots." Now more writers of color are penning sci-fi, fantasy and horror. Many were inspired by the late Octavia Butler, the first science-fiction writer to receive the MacArthur "Genius Grant" Fellowship.

The impact of Butler, who was black, is immense. She proved that a writer of color can write a successful sci-fi novel without shedding her racial identity. One of her most popular novels is "Kindred," which follows a contemporary black woman who is whisked back in time to 19th-century America, where she meets her ancestors. Contemporary writers of color such as Tananarive Due, Colson Whitehead and Walter Mosley ("Devil in a Blue Dress") have also written sci-fi and horror novels.

"It's liberating as a black woman to see yourself in the books of people like Butler and on TV," says Alexis Charles, a Stanford University graduate student who wrote an essay for the online magazine Salon called " The future can't be all white: Why Uhura and Beetee matter ."

"It's wonderful to see the diversity in characters, and to see someone who looks like me doing amazing things in the future and helping to create that future."

What shows are the most diverse?

So what shows do you turn on if you want to see this new racial sensibility?

Fans tend to cite the same ones: "Sleepy Hollow," "The Walking Dead," "Arrow," "The Vampire Diaries" and "The Originals."

When you look at any kind of monster ... they've always challenged our assumption that someone who doesn't look like us is someone to be feared. Gale Anne Hurd, executive producer of AMC's "The Walking Dead"

Some of these are breaking racial ground in a more daring way. They are casting people of color in roles that were traditionally written as white. It's a reversal of the practice of casting white actors such as Jake Gyllenhaal to play characters of color in films such as "Prince of Persia: The Sands of Time."

The CW Network show "The Vampire Diaries" selected a biracial actress to play a role written originally as a white, red-haired witch. The show is based on a series of young adult novels depicting the love triangle between two vampire brothers and a high school girl.

The actress, Kat Graham, gives a soulful performance as Bonnie, a witch who takes on vampires and werewolves to defend her friends.

Some "Vampire Diaries" fans will occasionally go online to complain about the diverse casting, but Julie Plec, the show's co-creator and executive producer, says they are a minority.

"I don't even bother to respond," she says, "because most of the fan base will respond for us and shut down the person."

The acceptance of racial diversity on sci-fi, fantasy and horror shows is so ingrained that Plec hesitated when asked if a show could get away with an all-white cast.

"It's possible -- they damn well better be all related," she says, chuckling.

Perhaps the most audacious example of this new post-racial landscape on TV is the character R.M. Renfield on the NBC show "Dracula."

In Bram Stoker's original 19th-century novel, Renfield was a white man. In virtually all Hollywood versions of "Dracula," he's been depicted as a demented white man slavishly devoted to Dracula. In the new TV series, Renfield is played by Nonso Anozie, a black British actor, as a fiercely intelligent and self-possessed man who earns Dracula's admiration.

The creator of NBC's "Dracula" says he decided early on that he would rewrite Renfield as a black man.

"As a nonhuman who is spurned and hated, Dracula would naturally have an affinity for black Americans who suffered oppression and alienation from society," says Daniel Knauf, the show's executive producer. "It was a natural choice."

Anozie says he's received "nothing but love" from fans.

"I have people doing things like making Renfield artwork and figures, right up to posting pictures of themselves ... with posters and my character," he says. "It's more intense than anything I've experienced."

Film, however, seems to be less receptive to this new racial sensibility.

Some people still want their big-screen heroes to be white men. There was an online uproar when the makers of the upcoming Marvel Comics "Fantastic Four" film selected Michael B. Jordan, a black actor, to play the Human Torch superhero. Fans also objected when Jeffrey Wright, a black actor, was picked to play Beetee, who was a white character in "The Hunger Games" book series.

Why it matters

The debate over a superhero's color may seem silly at first. Why should it matter if the Human Torch is black, brown or white -- he's a torch, big deal. But sci-fi, fantasy and horror stories do more than give people thrills. They can drive social change or slow its progress, some say.

"Will & Grace" and "Ellen," for example, were credited with helping ease acceptance of gays and lesbians by using comedy to normalize a group of people deemed different.

At that moment, the world tilted for me. That's all I could think of. "Star Trek" actress Nichelle Nichols after meeting the Rev. Martin Luther King Jr.

Similarly, sci-fi, fantasy and horror shows teach children about tolerance without being preachy because their young audiences are wrapped up in the stories, says Michael D. Baran, a cultural anthropologist who studies how youth learn about race.

"They're not going to get messages that a kid's worth is dependent on how they look," Baran says. "One of the things these shows don't do is come out and say 'everyone is equal.' As soon as kids feel like they're being taught something, they're wary about it."

When shows tell stories where marginalized groups are excluded from the stories a nation tells about itself, children get another message, says Hunt, director of UCLA's Bunche Center.

"At some point you start to normalize the notion that only white men can be the hero and only white men can be in charge," Hunt says.

That notion won't last though if more shows such as "Sleepy Hollow" get good ratings. Television will change because America is changing, Hunt says.

"As the audience gets more diverse, it's going to gravitate to more things that tend to be important to them," he says.

For all the talk about a racial awakening on TV, there's still one final frontier that's waiting to be crossed, says Anozie, the actor on "Dracula."

Perhaps one day a fan will boldly go where few have gone before when they talk about his roles.

"People often tell me how rare it is to be cast in the roles I have as a black man," says Anozie, who has also appeared in "Game of Thrones" and "Ender's Game."

"I guess things will have really changed when people compliment your work without having to mention skin color."