Scooby-Doo and The Phantom of Dume (Animated Movie)

When the gang visit a town, they realize strange things happening.

Characters:

 * Scooby-Doo (Frank Welker)
 * Shaggy Rogers (Matthew Lillard) - he and Scooby act like high school jocks during their mysteries
 * Fred Jones (Frank Welker)
 * Daphne Blake (Grey DeLisle)
 * Velma Dinkley (Mindy Cohn)
 * ??? (Danielle Judovits) - a resident of her hometown, who seeks from Mystery Inc.

Suspects:

 * Jack Curtis (Gary Cole) - a doctor, Reason: he and ??? were spied on Fred, Daphne and Velma doing a ritual, and then was captured and asked why, he reveals, ???
 * ??? (Stephen Root) - Reason: was performing a ritual with ???
 * ??? (Crispin Freeman) - a school jock who meets Shaggy, mistaken as a jock, and Scooby, mistaken as a mascot for ???, Reason: Shaggy and Scooby hear him and his friends ???
 * ??? (Caitlynne Medrick) - has the same tone as Total Drama's Dawn, ???'s best friend, Reason: she vanishes, floats in thin air, cares for Mother Nature, and she moved from a wet spot to a dry spot
 * ??? (Maurice LaMarche) - an FBI agent, who does his job, and warns Mystery Inc to stay off the FBI's back, has the same tone as Agent Steven Fullbright from Beverly Hills Cop 3, Reason: tells Shaggy and Scooby warningly that he and the FBI need to the job alone, and tells them to stay off their backs

Clues:
???

Culprits:
???

Plot:
???