When Bart jumps on Cecil's shoulders covering his eyes with his hands and says guess who, Cecil replies "Maris?" - David Hyde Pierce (who does the voice of Cecil) played Niles on the hit show _"Frasier"_. His wife on the show, who was never seen, was named Maris.
Sideshow Bob (Kelsey Grammer) and Cecil Terwilliger (David Hyde Pierce) are brothers in this coincidentally that Dr. Frasier Crane (Kelsey Grammer) and Dr. Niles Crane (David Hyde Pierce) are also brothers in the popular Cheers spinoff series, Frasier. The title of this episode of The Simpsons describes it.