Other mistake: The scene where Alice is giving Tiger a bath was the same one used in "Katchoo Katchoo", albeit with some audio dubbing thrown in, like when Alice complains about the floor getting wet. (00:04:05)
Other mistake: In the Y valley travel agents sketch Smoke Too Much states that he can't say the letter C. But he uses several Cs before Bounder suggests he uses the letter K, even saying "I can't say the letter B." He says that he'd never thought of the letter K before.
Don't Fool With a Phantom - S2-E8
Other mistake: When the wax phantom appears behind Scooby and Shaggy the man who supposedly is impersonating him in the suit is in clear sight directly behind Fred Daphne and Velma.
Other mistake: The banner over the platform says "Miss Vestal Virgin 79 B.C.", when it was earlier announced several times as the 72 B.C. Vestal Virgin festival.
Other mistake: Kenneth Cope had to wear a toupee for his part. He did so, only it was initially on the wrong way, though no one pointed it out or noticed. If it ain't broke...