Chandra the Unbelievably Remarkable and Quite Interesting Too is a witch who performs as a stage magician, one of the guests at Dracula's Halloween party.
She claimed to have summoned the Ghost of Dr. Van Helsing. Actually she was working with Igor, with a hidden motive to get the Moonstone Medallion, to give her enough magical power to take over the castle. Her plan backfired when she tried to turn Scooby into a toad. He ran fast enough to lead the spell back to her and transform her instead.