A Pup Named Scooby-Doo

S4 E1: The Were-Doo of Doo Manor

Scooby decides to go visit his family, though he soon discovers that they are all concerned with a curse that was supposedly placed on their family. The Scooby-Doo Detective Agency decides to investigate the curse in order to prove to the family that they have nothing to be concerned with, though they soon discover that there actually does seem to be a beast in their midst.