Tom and Jerry: The Movie (Chuck Jones)

Tom and Jerry: The Movie was a planned full-length movie version of the Tom and Jerry cartoon shorts, scheduled for release near the end of the 1960s. It was going to be produced and likely directed by Chuck Jones, who had produced a series of Tom and Jerry cartoons for MGM through his company Sib Tower 12 between 1963 and 1967.

Why It Was Cancelled

 * 1) Jones was never overly fond of Tom and Jerry to begin with, and directed them primarily so that MGM would fund projects he was more interested in, such as The Dot and the Line, The Bear that Wasn't, and various Dr. Seuss adaptations.
 * 2) Michael Maltese and Bob Ogle, who were the main writers for Jones' Tom and Jerry shorts, got hired away by Hanna-Barbera and DePatie-Freleng Enterprises respectively after production on the shorts ended, and Jones couldn't figure out how to work the format into a full-length movie by himself.
 * MGM, who were likely once again trying to get Jones to make a Tom and Jerry project before letting him make something else, relented and let him go straight to making an adaptation of the novel The Phantom Tollbooth, which was what he had wanted to do in the first place.

Results

 * Jones moved onto making his The Phantom Tollbooth operation, which under-performed commercially and resulted in MGM closing down their animation studio for the last time. He subsequently formed his own animation company, and worked there until his death in 2002.
 * A Tom and Jerry movie eventually was made over two decades later, being released in 1992 and directed by Phil Roman, who worked as an animator on several of Jones' shorts and The Phantom Tollbooth (and thus would almost certainly have worked on Jones' Tom and Jerry movie had it been made). However, it proved to be a critical and commercial failure. More Tom and Jerry movies would be made in the years that followed, but they were direct-to-VHS/DVD instead of theatrically-released.