Shirley McLoon is an agent of the Treasury Department. She pretended to be a psychic medium while she was undercover. Appearing in "A Bicycle Built for Boo!", an episode of A Pup Named Scooby-Doo, she was voiced by Isabel Sanford.
Shirley is a slender African-American female with short black hair, and wears sunglasses. She wears a red shirt and red pants, blue-green boots, and a purple overcoat. She also wears a red medium psychic's hat that has antennae and an eye on it (as part of her disguise).
She's dedicated to her job as federal agent with the Treasury Department, and takes on wild disguises (such as a psychic) to get the job done.
The Scooby-Doo Detective Agency encountered Shirley outside the Ferguson Estate, and found her wild persona to be suspicious. She had been locked in the mansion's cell by the ghost, and was rescued by the gang. It was revealed that she had been trying to bust the ghost, who was unmasked as Mr. Conrad, who was counterfeiting money. She then took him into custody.
- Shirley's name is a play on the famous New Age aficionado, Shirley MacLaine.
- Series producer/developer Tom Ruegger later reused the name for Shirley "the Loon" McLoon, a character on Tiny Toon Adventures (on which he was also a producer/developer), who was also into psychic powers and fortunetelling.