Cassidy-is one half of of the Team Rocket duo.
Cassidy is a high-ranking member of Team Rocket, along with her partner Butch. Cassidy is Jessie's nemesis and loves to put her and James down. Cassidy and Butch also have stronger Pokemon than Jessie and James.
Cassidy and Butch are Giovanni's favorites because they capture more Pokemon for him, unlike Jessie and James. Cassidy and Butch are also the founders of Team Rocket's breeding center and when stealing Pokemon, they always pretend to be Pokemon breeders that promise trainers that they'll take good care of their Pokemon for a while. But when the trainers come back, the center is empty and their prized Pokemon are being shipped to Giovanni.
Unlike Jessie and James, Cassidy and Butch are usually caught by the police and arrested for their attempted thefts. But also unlike Jessie and James, Giovanni himself comes to their rescue and bails Cassidy and Butch out of jail.