Larry Brantley, the voice of Wishbone, made an appearance in the episode "Rushin' to the Bone". He played the character Larry Brinkley, the man providing the voice to Wishbone's Scottish character "Mr. MacPooch" for a dog food commercial.
This series never featured any foxes or coyotes in Wishbone's "contemporary" stories. The titular Jack Russell terrier occasionally interacted with cats. He confronted a black cat in the Halloween episode "Halloween Hound: The Legend of the Creepy Collars".
Only the characters from Wishbone's literary daydreams and the audience can hear him speak throughout this entire series. The characters from Wishbone's daydreams view him as whatever famous character he portrays, not as a domestic dog.