She was vain and always looking in mirrors which disgusted even Joker.
She was helping the Joker in his new crime wave involving a machine he had invented called a "Magic Box" that could freeze time with the option of reversing and forwarding.
The Joker decides to use his new toy to terrorize Gotham and hold it ransom for $10 million. When Batman and Robin intervene, Cornelia helps Joker capture the Dynamic Duo and place them in the felonious funnyman's traps; Batman strapped to a giant key duplicator and Robin placed inside a spray wax machine. However thanks to Batman using an ordinary spare house key, he frees himself and Robin while the criminals escape.
Cornelia is then seen with Joker and his henchman heading for the Gotham Waterworks to infect the entire water supply however they are foiled by Alfred who took his look-a-like cousin Egbert's place as guard and managed to use Joker's box against them.
Batman and Robiin arrive and after a fierce fight, arrests Joker and his men. Cornelia is seen fleeing the scene during the battle but it is assumed that she was eventually arrested too.
- Kathy was married to Burt Ward (Robin) during the time the episodes were produced.