Right, Equus.
![Very Happy](https://cdn2.able2know.org/images/v5/emoticons/icon_biggrin.gif)
The ghost dog in the TV series was Neil, the St. Bernard.
But, the ghost dog in the movie, "Topper Takes a Trip" (1939) was Asta as Mr. Atlas. Roland Young and Billie Burke played Topper and his wife. Cary Grant and Constance Bennett were the ghosts.