Cecil Terwilliger is a villain on The Simpsons. He was the main antagonist of the 1997 episode Brother from Another Series and the secondary antagonist of the 2007 episode Funeral for a Fiend. He is the younger brother of Sideshow Bob, and son of Robert Terwilliger Sr. and Dame Judith Underdunk. He also has a sister-in-law named Francesca Terwilliger and a nephew named Gino Terwilliger. He is voiced by David Hyde Pierce.