Estelle is an X Middle School student.
In , after Fillmore and Ingrid discovered an orange Dancey Lads pin button and a bag of what was supposedly flour that Brad Parnassus had been using, they went to Estelle's house to find out if she happened to know anything about them. She told them that she'd been missing a pin button that belonged to her, as well as a black sweater, and wanted the pin button back. But Fillmore and Ingrid had to keep it for evidence. Then, they asked her about the empty bag of flour. Estelle told them the bag was filled with stink bomb powder, which was really what Brad had been using.
Estelle is voiced by Debi Derryberry.