Special Delivery Kluger is the narrator of the Rankin/Bass Christmas television special Santa Claus is Comin' to Town.
S.D. later reappeared as the narrator in another Rankin/Bass holiday special - The Easter Bunny is Comin' to Town, in which he answered questions about the origins of the Easter Bunny and also drives a steam train named Chugs (who is the famous "Little Engine That Could", whose story is also adapted as part of the special). This special notably revealed that S.D. was a citizen of Kidville in his youth.
The character is a caricature of his performer, Fred Astaire.