|First Appearance||Reverse Cowgirl|
Clyde Donovan's sister is a secretive girl who was first mentioned when Betsy Donovan was dying in a toliet bowl, begging her son to keep the seat down for his sister's sake. Whether or not she appears at her mother's funeral is debatable.
- Reverse Cowgirl (s16e01; mentioned)
While neither character has been explicitly said to be Clyde's Sister, either of the following may be her, until an image is added by the admins:
- A teenage girl voiced by Trey Parker can be seen in the deleted scenes for "Reverse Cowgirl" singing at Betsy Donovan's funeral - it's possible this is Clyde's sister.
- Clyde is also seen sitting next to an older woman with brown hair in all-black at the funeral who might be his sister.