The memorable "Aaaugh!" scream from Peter Robbins as Charlie Brown originated from this film. (Oddly enough, it was also heard from Linus in one scene.) Robbins' scream would become a stock sound effect in almost all subsequent Peanuts specials & movies up to the late 1990s, and is used as a scream, not only for Charlie Brown, but any other available character (excluding Snoopy and Woodstock, who had their own variants).
The main story line of this movie, involving Charlie Brown's participation in a spelling bee, was taken from a sequence that originally appeared in the comic strip. In that story, however, Charlie Brown lost in the first round of the competition, misspelling the word "maze" M-A-Y-S. He later loses his temper at the teacher and is sent to the principal's office; as he waits in the hall, he reflects that the reason he misspelled the word was that when he heard the word "maze," the first thing he thought of was the surname of famed baseball player Willie Mays. This last half of the story had been used in You're in Love, Charlie Brown (1967), when Charlie Brown inadvertently yelled at the teacher for "missing the stupid bus" (after he overslept).
Peppermint Patty makes a brief appearance in one shot (behind Frieda), among a group of children cheering for Charlie Brown upon successfully spelling "perceive" in the class spelling bee. She would finally become a major character in the next film, Snoopy Come Home (1972).