The Secret Files of the Spy Dogs S01 E10 "Fetch" or "The Secret File of the Paleozoic Puppy"

Ralph becomes impatient with his master's wanting to play Fetch. But then Ralph has a flashback and remembers how the game of Fetch came to be, as told by his old teacher, Dahg Chow. The story relates to the very first Spy Dog, of the name "Fetch."