Vince Guaraldi sung the vocals for the song "Little Birdie", one of the rare moments he lended his voice to the music he created for the Peanuts specials, the other being "Joe Cool" in "You're Not Elected Charlie Brown" from 1972.
Peppermint Patty and Marcie are voiced by male actors.
Lucy appears only at the beginning of the film when she is playing football with Charlie Brown. After that she disappears for the rest of the movie.
When Peppermint Patty informs the gang that they're invited to Charlie Brown's grandmother's house, this is one of the very few times she calls him "Charlie Brown" instead of "Chuck."
Snoopy's fight with the folding lounge chair appears to have been inspired by W. C. Fields' similar struggle with a chair in 1934's "It's A Gift."