Dr. Robert Terwilliger, Sr., also known as Dr. Robert, is Robert and Cecil Terwilliger's father. When Sideshow Bob was put on trial for trying to kill The Simpsons, he claimed that Bob had suffered from an illness caused by his desire to kill Bart Simpson. Bart threw Sideshow Bob's medication out of a window (believing it to be a biological weapon). This subsequently caused Sideshow Bob to "die". In reality, Bob was injected with a death simulation drug by his father prior to the fated trial in order to conduct a complex plan to kill Bart Simpson via locking him in a coffin and cremating him. He, and the rest of the Terwilliger family, were sent to prison afterwards.