|“||I forgot to mention, I'm planning to blow up the dam with you inside.||„|
|~ Cecil to Bob, Bart and Lisa|
Cecil Terwilliger is a recurring antagonist of The Simpsons. He is 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 his sister-in-law named Francesca Terwilliger and his nephew named Gino Terwilliger.
He was voiced by David Hyde Pierce.
Cecil felt deeply jealous of his older brother Bob, because as children, Cecil was ignored repeatedly by his parents, and instead compared to Bob. As adults, Bob and Cecil didn't talk to each other for years, because Cecil wasn't chosen for Krusty's show during the sideshow auditions. Krusty, Cecil's childhood hero, considered Cecil too unfunny, as soon as he noticed Bob, he chose him as his new sidekick. (Ironically, despite being Cecil being jealous of Bob for getting the part instead of him, Bob later decided to frame Krusty so he could create his own show).
As his introduction story progresses, we discover that he has also hidden criminal behaviors, which have rooted from his jealousy against his brother after what happened in the auditions. As the episode progresses on, Bart and Lisa learns of an embezzlement scheme that will endanger the local hydroelectric dam that is funded for it, and initially believed that Bob was the one who embezzled it, but Cecil reveals himself to be the true culprit as he is holding Bob, Bart, and Lisa hostage with a gun. It was then he revealed his true colors to frame Bob for the embezzlement scheme and blow the dam with him, Bart, and Lisa inside to get revenge for the audition incident walk away clean with the money.
Fortunately, Bob, Bart, and Lisa went on to work together to stop Cecil in his tracks and turned him over to the police, but unfortunately, Chief Wiggum arrests Bob as well, believing him to be involved. As both brothers are taken away, Cecil tricks Bob into swearing revenge on Bart for not defending his innocence, and as Bob fell for it, he realized he just made Bart his enemy again, and angrily holds Cecil responsible for it. Seconds after being imprisoned, the two childishly bickered over who got the top bunk, to which Bob won. Unfamiliar with prison, Cecil asked when the guards brought them menus.
When Bob was later arrested for attempting to kill the Simpsons again, he had taken out a vial of nitroglycerin. Bart, however, thought it was a bomb, and threw it out the window. Bob's father, Robert Terwilliger Sr., claimed it was a cure for Bob's heart condition. In truth, Bob never had any true medical conditions, and his father injected anesthesia into his body. During the "funeral", Cecil was temporarily released from prison on watch by parole officers to attend. After Bob's fake funeral, Cecil came to an unhappy Bart, and persuaded him to make his peace with Bob before his cremation. This led Bart to visit to the funeral house, only to be locked in the coffin by Bob who then tried to burn him up.
The plot was foiled by Lisa and the Simpson family arrived to stop Bob's family. They freed Bart from the coffin, and delayed Bob, Cecil, and the rest of the family by throwing ashes in their eyes. Chief Wiggum and the police arrived and arrested Bob, Francesca, Gino, their parents, as well as reincarcerating Cecil.
- As a homage to the television series Fraiser, Cecil is based on David Hyde Pierce's character Niles (brother of Kelsey Grammer's Fraiser Crane).
- Cecil could easily be the evilest villain of the series as he tried to flood the city and kill his brother and two children (Bart and Lisa). However, he is outranked by Russ Cargill, who is more dangerous and ruthless than Cecil.
- It is unclear if Cecil is still in prison, since his absence during scenes of his brother in jail. It is likely that Cecil had been released, paroled, or transferred to a different prison. It is also plausible that he escaped.