Haruhi Suzumiya (涼宮ハルヒ in Japanese) is a notorious light novel and anime series from Japan. The story features a cynical protagonist, a Mary Sue female lead, and generally every kind of character archetype that you'd see in a typical fanfic.
The book series presently includes 10 volumes, and is unfinished. The anime, primarily known under the name of The Melancholy of Haruhi Suzumiya (涼宮ハルヒの憂鬱 in Japanese, Suzumiya Haruhi no Yuuutsu to the weeaboo fanbase), spanned two seasons that only covered four of the books, and wasted half of one of those seasons covering a very short portion of the fifth novel.
This second season is notable for being a spectacular example of trolling on the part of Kyoto Animation. After getting the fanbase hyped by teasing a second season for over a year, they then spent two-thirds of that season repeating one episode eight times (with slightly different details each time, as if to prove that they were trying to piss people off rather than being lazy), as an adaptation of a very short, Groundhog Day-esque short story (Endless Eight). Needless to say, the fans' rage was spectacular. Many former Haruhi diehards started flipping out, and one Japanese fan went so far as to tear up his collection of the novels, smash a huge, expensive collection of figurines of the characters, and share the photos on the Internet. Even Kyoto Animation themselves were divided on whether this unexpectedly-successful trolling was a good thing or not, and it caused a falling-out within the studio that lead to the director of the series to leave and start his own studio (Ordet, currently known for the decidedly-mediocre Black*Rock Shooter and Fractale).
The series also had an anime movie called The Disappearance of Haruhi Suzumiya (涼宮ハルヒの消失 or Suzumiya Haruhi no Shoushitsu), which covered the entire fourth novel in the same amount of time one would take to read it.
There are various spinoff series of Haruhi too, with the most well-known one being Nyoro~n Churuya-san.
At the end of every episode of the original anime, the characters did a dance called the Hare Hare Yukai. This dance became really popular among weeaboos and huge Hare Hare Yukai flashmobs were in vogue for a short time.
In Japan, the first novel was published on June 3rd, 2003. The first short story of the series, The Boredom of Haruhi Suzumiya, was published in a Japanese novel magazine six months prior to the first novel.
Haruhi fandom has died down a bit in popularity in the years, owing to the fact that the anime is considered "finished." The last season especially killed the popularity due to the Endless Eight fiasco. That, and very few people feel the need to read books these days.
Fan translations of the books are still being done, along with official English publications.
- Lucky Star is mostly an ad for Haruhi merchandise.
Haruhi has an Awesome face!