Question: Waylon Smithers appeared an episode of The Simpsons that originally aired on January 21, 1990, and that has Homer promoted to what position?
Sentence (from "Waylon Smithers"): Waylon J. Smithers Jr., usually referred to as Mr. Smithers or simply Smithers, is a recurring fictional character in the American animated sitcom "The Simpsons", who is voiced by Harry Shearer.
Relevant evidence: No