Mrs. Dooberry was the disguise of Scooby-Doo.
Scooby disguised himself as a police woman, wearing a blond wig, lipstick, a police uniform and hat.
Scooby acted very strict and serious and threatened the ghost not to mess with him.
A Pup Named Scooby-Doo
When the gang was threatened by the Ghost of Mrs. Shusham, Scooby wore this disguise, pretending to be a book patrol officer and Mrs. Shusham had torn a page in a library book. This caused her to leave to take care of the problem.