The name of the first letter changes before Velma has even flipped through them, when the camera switches from faraway to close up.
When the Shadow Creature attacks Fred and the girls, he creates a gust of wind that comes from outside, but the wind is animated as if it's blowing in the opposite direction.
Velma explains the Shadow Creature's levitation power as being done with wires, but no explanation is given for his ability to create gusts of wind.