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?

<P0-S0> Gregory S. Butler (August 18, 1971, Suffield, Connecticut) is a visual effects supervisor. <P0-S1>  He graduated from Suffield High School in 1989 and afterwards entered Hampshire College. <P0-S2>  Despite his initial plans to study history, a work-study job with the audiovisual equipment in the library made him interested in film production. <P0-S3>  Butler graduated in 1993 with a major in film, television and theater design. <P0-S4>  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". <P0-S5>  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". <P0-S6>  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". <P0-S7>  His biggest achievement was working in the creation of Gollum. <P0-S8>  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. <P0-S9>  He continues on MPC, but is now on the Vancouver office. <P0-S10>  On January 24, 2012, he was nominated for an Academy Award for "". <SEP> <P1-S0> Gollum is a fictional character from J. R. R. Tolkien's legendarium. <P1-S1>  He was introduced in the 1937 fantasy novel "The Hobbit", and became an important supporting character in its sequel, "The Lord of the Rings". <P1-S2>  Gollum was a Stoor Hobbit of the River-folk, who lived near the Gladden Fields. <P1-S3>  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". <SEP> <P2-S0> Aragorn II, son of Arathorn is a fictional character from J. R. R. Tolkien's legendarium. <P2-S1>  He is one of the main protagonists of "The Lord of the Rings". <P2-S2>  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". <P2-S3>  He was eventually discovered to be the heir of Isildur and rightful claimant to the thrones of Arnor and Gondor. <P2-S4>  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. <SEP> <P3-S0> Dori Hillestad Butler (born August 26, 1965) is an American author of children's books. <P3-S1>  She has written more than 40 children's books, as well as magazine stories, plays and educational materials. <P3-S2>  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. <P3-S3>  Her 2010 mystery title, "Buddy Files: Case of the Last Boy", won the 2011 Edgar Award for the best juvenile mystery published in 2010. <P3-S4>  Prior to becoming a children's author, Butler worked for three years as a page at a library. <P3-S5>  She is married with two sons. <P3-S6>  The family lives in Kirkland, Washington.