Sideshow Bob's hidden family is a tribute to the series Frasier

The character of Cecil, Sideshow Bob's brother, was created by drawing inspiration from the relationships in the series Frasier. He is also voiced by David Hyde Pierce, who already played the brother of Kelsey Grammer, the performer of Sideshow Bob. Furthermore, the father of the two brothers is played by John Mahoney, who also played the father of the two actors in Frasier.