Question: While working on "The Lord of the Rings", Greg Butler worked on the effects for a fictional character first imagined by what famous author?

Context paragraphs:
Greg Butler (visual effects supervisor): Gregory S. Butler (August 18, 1971, Suffield, Connecticut) is a visual effects supervisor.  He graduated from Suffield High School in 1989 and afterwards entered Hampshire College.  Despite his initial plans to study history, a work-study job with the audiovisual equipment in the library made him interested in film production.  Butler graduated in 1993 with a major in film, television and theater design.  Afterwards he moved to California to work for Industrial Light and Magic for 9 months, where after intern work he managed to become an assistant in the effects department, starting with assistant credits in "The Mask" and "Forrest Gump".  Following a job at Rocket Science Games until the company's bankruptcy in 1996, Butler went to Tippett Studio and did effects work in "Starship Troopers" and "My Favorite Martian", rising up to a technical director job, and Cinesite for "Practical Magic".  While reluctant at the requirement of moving to New Zealand, Butler was convinced by his writer-actor brother Jared to jump at the opportunity of working for Weta Digital in "The Lord of the Rings".  His biggest achievement was working in the creation of Gollum.  Butler also worked as a computer graphics supervisor on "I, Robot" before an invitation to work as an effects supervisor for the Moving Picture Company, in London.  He continues on MPC, but is now on the Vancouver office.  On January 24, 2012, he was nominated for an Academy Award for "".

Joan Bauer (novelist): Joan Baehler Bauer (born July 12, 1951) is an American writer of young adult literature currently residing in Brooklyn.  Bauer was born in River Forest, Illinois.  She settled down in New York City with her husband Doug Langham.  They later became parents to one daughter, Jean.  Before becoming a famous author Joan spent years working for McGraw-Hill and the Chicago Tribune.  She also did some work in advertising, marketing, and screenwriting.

Aragorn: Aragorn II, son of Arathorn is a fictional character from J. R. R. Tolkien's legendarium.  He is one of the main protagonists of "The Lord of the Rings".  Aragorn was a Ranger of the North, first introduced with the name Strider at Bree, as the Hobbits continued to call him throughout "The Lord of the Rings".  He was eventually discovered to be the heir of Isildur and rightful claimant to the thrones of Arnor and Gondor.  He was also a confidant of Gandalf and an integral part of the quest to destroy the One Ring and defeat the Dark Lord Sauron.

World Book Club: World Book Club is a radio programme on the BBC World Service.  Each edition of the programme, which is broadcast on the first Saturday of the month with repeats into the following Monday, features a famous author discussing one of his or her books, often the most well-known one, with the public.  Since the programme began in 2002 it has been presented by Harriett Gilbert .

Hussein Barghouthi: Hussein Jamil Barghouthi, also spelled Barghouti, ( May 5, 1954 – May 1, 2002, Arabic: حسين جميل برغوثي‎ ‎ ) was a Palestinian poet, writer, essayist, critic, lyricist, play write and philosopher, born in the village of Kobar in the Ramallah and al-Bireh Governorate.  Barghouthi lived his childhood between Kobar, where his mother lived, and Beirut, where his father worked.  An outcast since childhood, seen and treated by his society as different and distant for being unique, he found his friends to be the rocks and trees of his village, and the words of his language.  He was misunderstood by his surroundings, and was too different from his society by the time he reached his last year in highschool, when he read out loud one of his poems for the first time in a poetry contest.  The contest was held by Jordanian education ministry, during the Jordanian custody of the West Bank, and Barghouthi was deprived of 1st place because the ministry of education thought he had stolen a poem from some famous author.  "Ignorance is not an excuse" replied Barghouthi, in front of the live audience.  Barghouthi got his high school diploma from Amir Hassan School in Birzeit.

Conan: Adventures in an Age Undreamed Of: Robert E. Howard's Conan: Adventures in an Age Undreamed Of, or simply Conan: Adventures in an Age Undreamed Of, is a sword and sorcery British pen-and-paper role-playing game set in the world of Conan the Barbarian, the fictional Hyborian Age.  Both the character and the setting were first imagined by American author Robert E. Howard (1906-1936) as of 1932 and until his suicide in 1936.  Howard's original literary work has since spawned a vast franchise of novels, comic books, films, video games, board games, role-playing games, etc.  Following this tradition, "Conan: Adventures in an Age Undreamed Of" is the third officially licensed Conan role-playing game.  The two precedent games were "Conan Role-Playing Game" (1985-1988) and "" (2004-2010), although there also had been supplements for independent generic systems, like "GURPS Conan" (1988-1989).

Bokprogrammet: Bokprogrammet is a Norwegian TV series on literature, which was shown on NRK1 from 2006 to 2014.  The programme looked at writing with a famous author, or at a theme or genre.  The programme was presented by Hans Olav Brenner for the first few years, and by Siss Vik from 2010 onwards.

Dori Hillestad Butler: Dori Hillestad Butler (born August 26, 1965) is an American author of children's books.  She has written more than 40 children's books, as well as magazine stories, plays and educational materials.  She is known particularly for "The Truth about Truman School", a 2008 young adult title focusing on the subject of cyber bullying, and for My Mom's Having a Baby (illustrated by Carol Thompson), which in 2011 appeared on the American Library Association's list of most challenged books for its portrayal of conception and childbirth.  Her 2010 mystery title, "Buddy Files: Case of the Last Boy", won the 2011 Edgar Award for the best juvenile mystery published in 2010.  Prior to becoming a children's author, Butler worked for three years as a page at a library.  She is married with two sons.  The family lives in Kirkland, Washington.

Gollum: Gollum is a fictional character from J. R. R. Tolkien's legendarium.  He was introduced in the 1937 fantasy novel "The Hobbit", and became an important supporting character in its sequel, "The Lord of the Rings".  Gollum was a Stoor Hobbit of the River-folk, who lived near the Gladden Fields.  Originally known as Sméagol, he was corrupted by the One Ring and later named Gollum after his habit of making "a horrible swallowing noise in his throat".

William Hamilton Gibson: Gibson was born in Sandy Hook, Connecticut, of an old, distinguished New England family; one of his great-great-grandfathers was the jurist Richard Dana (1699–1772), who was the great-grandfather of the famous author Richard Henry Dana, Jr. The financial failure and in 1868 the death of Gibson's father, a New York broker, put an end to his studies in the Brooklyn Polytechnic Institute and made it necessary for him to earn his own living.  From the life insurance business, in Brooklyn, he soon turned to the study of natural history and illustration, he had sketched flowers and insects when he was only eight years old, had long been interested in botany and entomology, and had acquired great skill in making faux flowers.  His first drawings, of a technical character, were published in 1870.

Supporting paragraphs: Greg Butler (visual effects supervisor) Gollum
Answer: J. R. R. Tolkien