This special is one of many that Violet and Patty are reduced to silent cameos. These two characters (among others like Shermy, Pig Pen, and Frieda) were prominent in the earlier specials, such as It's the Great Pumpkin, Charlie Brown (1966) and A Charlie Brown Christmas (1965), but were phased out with the introduction of Peppermint Patty and Marcie.
The side story of Charlie Brown having to do a book report was taken from a series of strips where the book in question is Gulliver's Travels. Like in the strip Charlie procrastinates so long on the report that he doesn't finally get it finished until 3AM the day it's due, and also got a D-minus on it.