The Cruel Veterinarian is the main antagonist in the episode Remembrance of Courage Past.
He acts like a kind old man, but in reality he is cruel and insane, believing that sending dogs into outer space would make them superdogs. This has led him to send many dogs into space against their will, including Courage's parents.
He was the one responsible for separating Courage from his parents as a puppy. He captured them, put them in a rocket ship, and sent them to the moon, believing they would turn into superdogs. However, Courage escaped from this fate and was adopted by Muriel.
Remembrance of Courage Past
Years later, he tries to do the same to Courage. When Muriel and Eustace attempt to rescue Courage, he decides that he can't allow his operation to be discovered and decides to send Muriel and Eustace into space as well. However, Courage rescues his owners and locks the vet inside the rocket and he is sent to the moon himself, where he finds that all the dogs survived, including Courage's parents. He was then brutally mauled by the dogs off screen.
- It's ironic, but in a way, fitting, that the first monster that Courage ever faced in his life is an ordinary human, especially a veterinarian.