Final answer:
David Hyde Pierce voiced the character Cecil Terwilliger on 'The Simpsons', where he played the brother of Sideshow Bob, voiced by Kelsey Grammer.
Step-by-step explanation:
Actor David Hyde Pierce portrayed the character of Cecil Terwilliger on the show The Simpsons. Similar to his role as Niles Crane on 'Frasier', Cecil Terwilliger is presented as the brother of another main character, in this case,
Sideshow Bob, who is voiced by Kelsey Grammer. The Simpsons is an animated television series known for its wide array of guest stars, including many who have played recurring characters.