A Scooby-Doo Valentine - S3-E3
Plot hole: It's never explained how JC Chasez and the Hollywood extras impersonating the gang gained the super strength they possessed to do things like ripping car roofs open or holding up the Mystery Machine.
Starring: Frank Welker, Grey DeLisle, Mindy Cohn, Casey Kasem
A Scooby-Doo Valentine - S3-E3
Plot hole: It's never explained how JC Chasez and the Hollywood extras impersonating the gang gained the super strength they possessed to do things like ripping car roofs open or holding up the Mystery Machine.

Continuity mistake: When the gang arrives at the fashion show, they park the Mystery Machine at the end of the walk way. But when the head of the fashion show is shown, the Mystery Machine has vanished. (00:03:05)
Answer: Because of the goo that was on it.