Lassie: The Wayfarers(1964)

Young Timmy Martin's world falls apart when he learns that his family must move to Australia. Lassie is to remain in America, so the Martins search for a new home for the Collie. Neighbor Cully Wilson takes Lassie in, but the old man already has a dog, the cheeky Yorkshire Terrier named Silky. Lassie is now constantly occupied with keeping the small dog in check.