For those not bitten by the vampire bug, the whole thing may seem a little silly. Blood-sucking, night-crawling creatures are just a fad, right? Think again - franchises like "Twilight," "True Blood," and even parodies like "Vampires Suck" are raking in the millions at a time when discretionary spending is low. Here is a look at some of the top-grossing vampire entertainment investments, and reasons why they're so successful. (Success in Hollywood isn't just measured by ticket sales. Check out Movie Genres That Make The Most Money.)

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  1. Twilight Saga
    It's hard to imagine when you see how successful the Twilight Saga is today, but it all started with a simple idea. Author Stephenie Meyer was a stay-at-home mom who had a dream with such vivid characters, she just had to write the story we now know as "Twilight". "Twilight" was followed by "New Moon," "Eclipse" and "Breaking Dawn," and Meyer also wrote a book for adults called "The Host". The Twilight Saga, though intended for teens, has captured a wide audience of all ages.
    So what did this stay-at-home mom's idea gross? Book sales have been wildly successful, selling millions of copies of the series, with book sales estimated at 100 million copies. Movie sales of the first three Twilight Saga movies, including DVD sales, have grossed an estimated over two billion. With at more movies in the works covering the "Breaking Dawn" book, and large merchandising earnings estimated at $500 million, the Twilight Saga is the entertainment industry's answer to the end of the Harry Potter series. Stephenie Meyer's net worth is an estimated $125 million - not bad for a dream. (Learn more about the top films in Top 10 Successful Movie Franchises.)

  2. Buffy The Vampire Slayer
    Teen Twilight fans may think that the series invented vampires, but the genre has made money long before the first book in the Twilight series even made print. Twilight fans' parents probably remember "Buffy the Vampire Slayer". The 1992 movie made close to $17 million; in 1997, a TV series was launched starring Sarah Michelle Gellar, which prompted spinoff "Angel" and gained a huge cult following even beyond its last episode in 2003.

  3. Interview with the Vampire
    Twilight fans were still in diapers when this movie came out, though it made big waves in 1994 as Brad Pitt and Tom Cruise's careers were solidified with the movie. As with the Twilight Saga, movie sales boosted book sales of the same-titled 1976 novel by Anne Rice, and elevated the author's career and future book sales. The movie grossed $105 million in the U.S. and another $118 million internationally, proving that vampires sell across the world and throughout the decades.

  4. The Vampire Diaries and True Blood
    It's obvious from Twilight's success that there's money to be made by telling vampire stories, which has prompted some TV series, like CW's "Vampire Diaries" and HBO's "True Blood". (Learn about another big money TV show in LOST: Behind The Numbers Of A TV Phenomenon.)
    In "True Blood"'s case in particular, what could have been a watered-down version of Twilight has become a series with a whole new vampire-loving audience ready to spend money to see what happens next. These series are still in their infancy, so it's too soon in their run to tell what money they'll generate. Entertainment experts estimate each series could generate an average $90 million and up once foreign licensing starts taking off.

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  1. Vampires Suck
    If you're getting a little sick of all things vampire, you're not alone - which is why 20th Century Fox released "Vampires Suck" in August of 2010. The movie pokes fun at all the vampire clichés, and rakes in the bucks at the same time: "Vampires Suck" grossed close to $36 million, with DVD sales likely to boost this number significantly. In this case, poking fun at a trend can mean big business too. (A good movie doesn't necessarily make money. Learn more in Money-Making Movies With Terrible Reviews.)

The Bottom Line
So where does this huge trend come from? Vampires aren't exactly a novelty - remember Bram Stoker's "Dracula," a novel published in 1897? The current vampire trend was undoubtedly spawned by the success of Stephenie Meyer's "Twilight," and the clever movie marketing and merchandising to teens with disposable income. Maybe it's the blend of romance, fantasy and horror that make vampire entertainment so profitable. Maybe it's the expanded internet marketing and merchandising of the 21st century. Either way, expect more vampire entertainment and spinoffs as long as there's money to be made - an estimated $7 billion for Hollywood so far - proving that fangs are big bucks.

For the latest financial news, check out Water Cooler Finance: The End Of The Recession.