Factual error: At one point in the film there is footage on the news of Mystery Inc's embarrassing attempt to stop the ghouls from stealing costumes. In particular, it focuses on Shaggy and Scooby being dragged across the table, etc. But look at the angle it's taken from: no one could have taken that.
Visible crew/equipment: When Fred and Daphne are held by the Tar Monster, you can see a crew member hiding in the background.
Continuity mistake: C.l Magnus takes the cigarette out of his mouth three times.
Answer: Yes! There was a real Heather Jasper Howe! Like the fake Heather Jasper Howe's True Identity is Jonathan Jacobo! He was arrested with Ned.
No, there is no real Heather Jasper Howe. The movie never shows that.