Dreyfuss is Harry Weston's dog and appeared primarily on the spin-off series Empty Nest. Dreyfuss and Harry live in the same Miami neighborhood as Blanche, Dorothy, Rose and Sophia. Dreyfuss appeared in several later-season episodes of The Golden Girls. Dreyfuss' breed is not confirmed throughout the series, but fairly certain that it was a Golden Retriever St. Bernard mix.
I thought it was a Leonberger.