Dilliss is a short, round woman with shoulder length grey hair and lighter colored bangs that cover her eyes. She wears a pink t-shirt and black pants with dark red ballet flats. Dilliss also wears pearl earrings and has large, red lips.
Dilliss was the wife of Seymour. She has an overbearing personality which causes Mary to keep her distance. Dilliss may have made her first appearance in "Patients" when she appears in Clarence's imagination (though it is unclear whether this was another one of his grandmothers as they did not look alike). She later appears in "Hurricane Dilliss", creating havoc when she decides to visit her daughter. Dilliss mentions that she hasn't seen Clarence is two years and appears unimpressed with Mary's boyfriend, Chad. Dilliss' manic, erratic behavior (including being missing for two days, messing up the house and spoiling all the food) eventually causes Mary to lose her patience. Though her behavior is far from normal, Dilliss did try to be helpful. However, she died shortly before "Plane Excited".
- "Jeff's New Toy" (mentioned only)
- "Man of the House" (mentioned only)
- "Nothing Ventured" (Picture seen)
- "Hurricane Dilliss" (only major role)
- "Hoofin' It" (mentioned only)
- "Plane Excited" (mentioned only)
- "Clarence Loves Shoopy" (cameo)
- Her name is revealed in "Hurricane Dilliss".
- The episode also features her only major role.
- A character known as "Clarence's grandmother" also appears in "Patients", though this grandmother's design was much different than Dilliss' in "Hurricane Dilliss". There are many explanations for this, including her being another of Clarence's grandmothers (probably Damian's Mom), that Clarence forgot what she looked like, or, as it was an imagination sequence, the grandmother was not supposed to look like her.
- She is now deceased as of "Plane Excited".
- She is the only or first character that have died so far in the Clarence series.
- She is implied to be senile.
- Strangely, she made a cameo on Clarence Loves Shoopy, despite her death in Plane Excited.