When Shaggy and Scooby are first seen peeking out of the filing cabinet, it is clearly standing on it's own, but when the ghost stands next to it in the very next shot, it's part of a complete row of cabinets, with no gaps between them.
Fred's sleeve is colored brown when he announces that it's time to trap the ghost.
A frozen solid hamburger is shown capable to make a floor crack, although in real life it's not sturdy enough to do such a thing.
When Shaggy unknowingly cooks a hamburger with the 10,000 Volt Ghost's electricity, he's somehow not electrocuted as the frying pan is made from iron, which is a perfect conductor to electricity. Not just that, that electrical power such as 10,000 Volts is more than enough to electrocute Shaggy (It's probably because the pan handler is covered in some kind of isolator, but it's not visible to the audience).