Dame Judith Terwilliger (née Underdunk) is the wife of Robert Terwilliger Sr. and the mother of Sideshow Bob and Cecil Terwilliger. According to Lisa, she is a retired Shakespearean actress. Her sons get their extremely curly hair from her. Though she looks like an elderly female version of Sideshow Bob, she and Cecil share a similar nose structure.
The title "Dame" means that she has been knighted, likely for services to theater.
- All members of the Terwilliger family are voiced by guest stars with the exception of Dame Judith and Gino.
|Ms. Albright | June Bellamy | Belle | Billy (actor) | Booberella | Colin | Cosine | Crazy Cat Lady | Michael D'Amico | David (Treehouse of Horror XVI) | Devan Woosterfield | Dia-Betty | Mia Farrow | Ginger Flanders | Mrs. Glick | Adil Hoxha | Bernice Hibbert | Cookie Kwan | Lester | Audrey McConnell | Medicine Woman | Mrs. Muntz | Lindsey Naegle | Manjula Nahasapeemapetilon | Opal | Poor Violet | Lois Pennycandy | Pepi | Phillips | Brunella Pommelhorst | Ronaldo (Blame It on Lisa) | Dr. Simpson | Agnes Skinner | Brandine Spuckler | Jitney Spuckler | Whitney Spuckler | Spud | Dolph Starbeam | Clara Stetson | Gino Terwilliger | Dame Judith Underdunk | Veronica | Vicki Valentine | Plopper|
|Robert Terwilliger Sr. | Dame Judith Underdunk | Sideshow Bob | Cecil Terwilliger | Francesca Terwilliger | Gino Terwilliger|