sentences:  The studio's roster of talent benefited from an exodus of animators from the Warner Bros. Cartoons and Disney studios, which were facing issues with union workers.Originally established and run by executive Fred Quimby, in 1955 William Hanna and Joseph Barbera, the writer-directors of the "Tom and Jerry" cartoons, became the heads of the studio.The cartoon studio was closed on August 1, 1958, at which time Hanna and Barbera took much of the staff to form their own company, Hanna-Barbera Productions.