Question: Who was the director of the film whose success, along with that of An American Tail and The Land Before Time, prompted Steven Spielberg to establish his own animation studio?
Context: An American Tail: Fievel Goes West (also known as An American Tail II: Fievel Goes West & An American Tail II) is a 1991 American animated comedy western film produced by Steven Spielberg's Amblimation animation studio and released by Universal Pictures.  It is the sequel to "An American Tail", and the last installment in the series to be released theatrically.  Two direct-to-video sequels were released in the late 1990s.  A continuation, "Fievel's American Tails", aired on CBS in 1992. Morris Francis Sullivan (December 8, 1916 – August 24, 2008) was an American businessman who co-founded the Sullivan Bluth Studios with three former Disney animators.  Sullivan Bluth Studios employed approximately 400 people at the peak of its success.  Under Sullivan's direction, the former animation studio created such films as "The Land Before Time" and "An American Tail". An event movie is a film whose release itself is considered a major event, such as an anticipated sequel or a big budget film with major stars generating considerable attention and state-of-the-art special effects.  An event movie is usually the highest-grossing box office movie in the particular year and becomes a part of popular culture.  Steven Spielberg's 1975 movie "Jaws" is considered the first event movie. Amblimation was the animation production arm of Steven Spielberg's Amblin Entertainment.  The studio was shut down in 1997 and some of the Amblimation staff went on to join DreamWorks Animation.  It was known for its quieter atmosphere, more subdued acting, and more atmospheric pace compared to a great deal of American animated films; these qualities usually led to underperformance at American box offices and may have factored in the decision to close the studio down.  The company's mascot, Fievel Mousekewitz ("An American Tail"), appears in its production logo.  It only made 3 films.  A project to adapt the 1981 Andrew Lloyd Webber musical "Cats" was in the making, but was abandoned with the studio's closure. []Mohanlal] is an Indian actor, producer, and singer who has starred in both blockbuster and art house films for independent filmmakers.  During his career, he has appeared in more than 340 feature films, primarily in Malayalam cinema but also in other languages including Hindi, Tamil, Telugu, and Kannada.  In 1978, when he was 18, he started acting with a minor comedic role in the unreleased film "Thiranottam", before making screen debut in 1980 as antagonist in the romance film "Manjil Virinja Pookkal".  His portrayal of Narendran, a sadistic husband, received recognition and the film developed a cult status in Malayalam cinema.  Subsequently, Mohanlal was cast as the antagonist in many films.  His first positive role was in "Padayottam" (1982), the first 70 mm film in Malayalam.  In 1984 he starred in "Poochakkoru Mookkuthi", a comedy film whose success triggered a trend and popularised the genre in the 1980s.  In an early critically acclaimed performance, Mohanlal played an antihero in the I. V. Sasi-directed thriller "Uyarangalil" (1984).  In the same year, he co-founded Casino Films, a motion picture production company which later produced his popular comedies "Gandhinagar 2nd Street" (1986) and "Nadodikkattu" (1987). Universal Animation Studios (formerly known as Universal Cartoon Studios) is an American animation studio which is a division of Universal Studios.  It is best known for producing sequels to Universal-released feature films, such as "The Land Before Time", "An American Tail", "Balto", as well as other films and television series. Balto is a 1995 American animated epic drama adventure film directed by Simon Wells, produced by Amblin Entertainment and distributed by Universal Pictures.  The film is loosely based on a true story about the dog of the same name who helped save children from the diphtheria epidemic in the 1925 serum run to Nome.  The live-action portions of the film were shot at Central Park in New York City.  The film was the third and final animated feature produced by Steven Spielberg's Amblimation animation studio.  Spielberg, Kathleen Kennedy and Bonne Radford acted as executive producers on the film.  Although the film's theatrical run was overshadowed by the success of the competing Pixar film "Toy Story," its subsequent strong sales on home video led to two direct-to-video sequels: "" (2002) and "" (2004) though none of the voice cast reprised their roles. An American Tail is a 1986 American animated musical adventure family comedy-drama film directed by Don Bluth and produced by Sullivan Bluth Studios and Amblin Entertainment.  It tells the story of Fievel Mousekewitz and his family as they emigrate from Russian Empire-controlled territory of Ukraine to the United States for freedom.  However, he gets lost and must find a way to reunite with them.  It was released on November 21, 1986, to reviews that ranged from positive to mixed and was a box office hit, making it the highest-grossing non-Disney animated film at the time.  The success of it, "The Land Before Time", and Disney's "Who Framed Roger Rabbit", as well as Bluth's departure from their partnership, prompted Steven Spielberg to establish his own animation studio, Amblimation. Who Framed Roger Rabbit is a 1988 American live-action/animated fantasy film directed by Robert Zemeckis, produced by Frank Marshall and Robert Watts, and written by Jeffrey Price and Peter S. Seaman.  The film is based on Gary K. Wolf's 1981 novel "Who Censored Roger Rabbit? " The film stars Bob Hoskins, Christopher Lloyd, Charles Fleischer, Stubby Kaye, and Joanna Cassidy.  Combining live-action and animation, the film is set in Hollywood during the late 1940s, where animated characters and people co-exist.  The story follows Eddie Valiant, a private detective who must exonerate "Toon" Roger Rabbit, who is accused of murdering a wealthy businessman. Steven Spielberg Presents Pinky, Elmyra & the Brain is the retooling of the animated television series "Pinky and the Brain" (itself being a spin-off from "Animaniacs"), with the title characters being joined by Elmyra Duff from "Tiny Toon Adventures".  The show is executive produced by Steven Spielberg and the series was produced by Amblin Television in association with Warner Bros.  Animation, and aired from 1998 to 1999 on The WB Television Network, running for 13 episodes.  It was Spielberg's last collaborative effort with Warner Bros.  Animation.
Answer: Robert Zemeckis