This is an abridged version of the original stage musical.
Three songs from the musical that were not featured in this movie were "My Blanket and Me," sung by Linus to his beloved security blanket; "The Doctor Is In," between Lucy and Charlie Brown at her famous psychiatrist's booth; and "My New Philosophy," sung between Sally and Schroder about Sally's ever changing philosophy.
Snoopy speaks for the first time in an animated special (voiced by Robert Towers, who was a member of the 1967 Los Angeles stage cast).
Some characters were changed in the transition from the stage. The original musical features only Charlie Brown, Linus, Lucy, Patty, Schroeder, and Snoopy. In the animated adaptation, Patty, no longer familiar to modern viewers, has been replaced by Sally. In the 1999 Broadway revival of "You're a Good Man," that change was kept (though Marcie, Peppermint Patty, and Woodstock also appear briefly as well, even though they aren't in the original).
Not to be confused with the February 9, 1973 Hallmark Hall of Fame TV broadcast on NBC-TV, which was live-action.