Veterinarian
Wikisimpsons - The Simpsons Wiki
The Veterinarian is an un named character who is the Doctor who performs Santa's Little Helper operation for a twisted stomach in "Dog of Death". In "So It's Come to This: A Simpsons Clip Show" and "Another Simpsons Clip Show", he appears in the hospital again. He has not appeared since Season 6's "Who Shot Mr. Burns? (Part One)", when he looks after Santa's Little Helper again.