During a visit to San Fransisco for the Grind Games, a world famous skateboarding competition, Scooby and the gang discover a monster known as the San Franpsycho. WHO is stalking the skaters?
Culprit: Rudy.
Reason: She wanted to get revenge at the Grind Games for not letting her enter. She thought it was because she was a girl, when actually she just couldn't skateboard.
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(As the gang, in a speedboat, are being chased by sharks)
Velma: We're gonna make it! (shark takes a bite out of the back of the boat, outboard motor and all) Ah, irony. We meet again.
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