Quote from : Rin Tin Tin: The Life and the Legend Book

Television wasn't getting rid of animals, but they were no longer cast as creatures that were omniscient and heroic. They were talking horses like Mr Ed or an absurdist pig like Arnold Ziffle...Just like the heroic animals in silent films became comedians in talkies, animals on television were becoming jesters, something Rin Tin Tin had never been.