The animated debut of Woodstock and Franklin.
The clown who takes Peppermint Patty and Charlie Brown's tickets at the Barrel O' Fun is a rare instance in the Peanuts franchise of an adult's face being visible.
The first "Peanuts" production without a musical score by Vince Guaraldi, who composed for all previous specials and the first and previous movie, A Boy Named Charlie Brown (1969). This was deliberate, as it was an experiment by Charles M. Schulz, who specifically wanted a more commercial, Disney-like feel for this film.
This was the first "Peanuts" production (as well as the only "Peanuts" theatrical feature until The Peanuts Movie (2015)) to not have the words "Charlie Brown" in the title.
One of the guests at Snoopy's goodbye party has the number five on his shirt. This is probably supposed to be 5, an easily forgotten character from the Peanuts strip whose whole family had numbers for names (including his sisters, 3 and 4). His full name is 5 95472 (the accent is on the 4).