Author Phobia

Authors are people just like us, with likes and dislikes... and fears. Sometimes a creator draws upon their personal Nightmare Fuel in an attempt to make their villains more fearsome and intimidating. For instance, if the author as a child was bitten by a venomous spider and nearly died, as JRR Tolkien was, they might make the Big Bad of their story a hideous Giant Spider.

Contrast Author Appeal.

Examples of Author Phobia include:

Anime and Manga

Yukito Kishiro is afraid of a certain kind of butterfly, and so is his character, Gally. This is only mentioned once.

Film

Peter Jackson actually used his own phobia of spiders to measure the effectiveness of Shelob's design and animations for the Lord of the Rings films.
James Cameron wrote The Terminator based on a nightmare he had of a robot emerging from a fiery explosion and coming after him. It's even referenced on the main Nightmare Fuel page quote. "From the director's nightmares to yours." However, Cameron was sued because the idea bore a resemblance to two Harlan Ellison-written The Outer Limits episodes, "Soldier" and "Demon with a Glass Hand". As part of the settlement, the credits of the movie now include the phrase "Acknowledgement to the works of Harlan Ellison."
H. R. Giger is known to have incorporated his nightmares into his creations. Apparently, he often worked through his sleeplessness.
Alfred Hitchcock had a fear of the police, thanks to an incident in his childhood where his father ordered a policeman to lock him up for ten minutes for being disobedient. As a result, Police Are Useless and Wrongly Accused were two of his favorite tropes.
Mel Gibson's films are heavily criticized in England and elsewhere for perceived Anglophobia - for instance, the historical villain upgrades given to Banastre Tarleton in The Patriot and Edward I in Braveheart (his record is far more mixed than Gibson suggests). Then there is his butchery of Gallipoli in the film of the same name, specifically the idea that the British drank tea on the beach whilst the Australians died for them. We will not mention his treatment of another group in another film...
A Nightmare on Elm Street: Wes Craven named Fred Krueger after a bully who harassed him and based his appearance on a disfigured hobo who scared him as a child.

Literature

JRR Tolkien was bitten by a poisonous spider in his youth in South Africa and narrowly escaped death. Many of his works feature giant, malevolent arachnids, including the spiders of Mirkwood, Shelob, and Ungoliant.
Much of what HP Lovecraft wrote was motivated by his own nightmares and personal phobias. Among the ones less likely to evoke similar feelings in readers nowadays were his fears of non-white Anglo-Saxon people and miscegenation. And fish. He also had a lifelong fear of cold temperatures, encouraged by his frail constitution. This is partly why the oppressive atmosphere of At the Mountains of Madness is so effective.
Stephen King is known for writing about things that scare him personally.
- In Particular, Pet Sematary is full of Adult Fear and based on a real incident where King stopped his son from almost getting run over by a truck. He couldn't shake thoughts of what would have happened if he failed, and wrote a novel around it.
Winston's fear of rats and its use against him in the Room 101 scene in Nineteen Eighty-Four was inspired by George Orwell's personal fear of rats.

Video Games

Chain Chomps came from an experience Shigeru Miyamoto had as a child, when a dog chased after him as he approached but stopped just inches from him because the dog was tied to a stake.
A particularly well-known example shows up in EarthBound, particularly in the form of the final boss, Giygas. According to Shigesato Itoi, the dialogue Giygas says is based off a childhood memory of him watching what he interpreted to be a rape scene (actually a sex followed by murder scene) in a movie.

Webcomics

Played for Laughs in xkcd by creator Randall Munroe, who apparently has a morbid fear of raptors.
Amber Williams of Dan and Mab's Furry Adventures is afraid of horses, which is why Kria and Dark Pegasus are both demonic horses.