When diehard fans watched TV shows and went, "Well, I can do that better" and took to the omnipotent internet to publish their fictionalised stories on already fictional characters, the incorrigible world of fan fiction was created.

Fan fiction was originally popularized by Trekkies, who dedicated themselves to filling the holes left by the plot of the original Star Trek TV series. And "fill in the holes" they did, as a huge chunk of these fan fictions focus on cavalier sex involving every character combination imaginable.

The most invested fans, frustrated with the fading out of characters after some tasteful kissing, quickly rush to their keyboards to pound out a scene of physical intimacy with all its gory details, often unsullied by familial relationship, age, sex or even species.

Here are four popular TV shows that has been written and rewritten by fans all over the world.

Glee

Glee
Gleetwitter/Glee

The TV show that enjoys the largest fandom is the musical comedy-drama television series "Glee" that focuses on the fictitious William McKinley High School glee club New Directions and its disparate members. Fans of the show, who call themselves Gleeks have created portmanteaus of character couples, such as "Finchel" for Finn and Rachel, "Klaine" for Kurt and Blaine, and "Brittana" for Brittany and Santana, and are not afraid to digress from the actual series plot and write new layers for the characters. For example, in a popular fanfic, Blaine is introduced as a hitchhiker Kurt picks up on the road and in another they run into each other five years post McKinley days, but Blaine is married with a child.

The four girls in the show are popular subjects for femslash fan fictions and are tagged "Faberrittana" (Quinn Fabray, Rachel Berry, Brittany and Santana).

Supernatural

Supernatural
Supernaturaltwitter/Supernatural

"Supernatural", a drama/action series follows the Winchester brothers, played by Jared Padalecki and Jensen Ackles, as they hunt demons, ghosts, monsters, angels and other supernatural beings. The show enjoys a dedicated fanbase that consistently flood fanfiction sites. A section of these writers solely focus on writing stories involving a sexual relationship between the brothers — popularly known as "Wincest".

"Destiel" is another favourite subject among fan fiction writers. The writers had all but thrown the possibility of this couple, complete with flirty lines and borderline seductive looks. In one episode, when Castiel looks at Dean in anger, the latter says, "The last time someone looked at me like that, I got laid."

Buffy The Vampire Slayer

"Buffy the Vampire Slayer" follows the life of Buffy Summers (played by Sarah Michelle Gellar), the latest in a line of young women known as vampire slayers, who are chosen to battle vampires, demons and other forces of darkness.

Simply type "Buffy the Vampire Slayer" into Google and over 1,800,000 entries come up, while searching for its fan fiction will pop up an additional 95,000+ entries. The loyalty and enthusiasm of Buffy fans impressed the creators so much, that in episodes such as "Something Blue"- where Buffy and Spike get married- and "Dopplegangaland" – where Willow's vampire twin express an interest in her,  unusual relationships that had been hinted on fan fiction websites were bought to reality.

Sherlock

"Sherlock" is a crime drama that presents a contemporary adaptation of Sir Arthur Conan Doyle's Sherlock Holmes stories with Benedict Cumberbatch playing Holmes and Martin Freeman as Doctor John Watson.

"Sherlock" enjoys a huge fan base spread throughout the world, who rally for the show audibly and visibly in the internet world through podcasts and fan fictions. Cumberbatch himself attributes the show's success to its "very intelligent, very loyal" fans and admitted that he is "startlingly aware" of the extensive collection of creative and explicit fan fiction that has surfaced online since the premiere of the show's first season. "There's some really weird cross breeding stuff that goes on," he said during an interview with MTV.