Its The Easter Beagle Charle Brown (1974)
With Easter coming up, the gang is hard at work for get ready for the holiday. While Snoopy is shopping for a new home for Woodstock, Peppermint Patty is having a difficult time making Easter eggs with Marcie who hasn't the slightest idea of how to do that.
"Linus says the Easter Beagle passes out eggs to all the kids on Easter. But I bet all he ends up with is egg on his face." Will he, or won't he...thereby hangs a tail!
Charlie Brown: I know why they have holidays. They have holidays so people can get together and have fun. So why am I alone?
Had Snoopy, as the Easter Beagle, thrown just one less egg on the ground when he first arrived, he would've had an egg for Charlie Brown.
According to Charles M. Schulz, the bunnies that Snoopy dances with are the Bunny-Wunnys, the characters from Snoopy's favorite children's book series.
The song that the music boxes play (and which Peppermint Patty, Marcie, and Snoopy dance to) in the second scene in the mall is a classical piece written by Johann Sebastian Bach and entitled "Minuet from the Anna Magdalena Notebook (BWV Anh. 116.)."
When the gang visits the mall, a sign proclaims it is 246 days until Christmas. Assuming the film's events take place in the year of its release, the date is April 23rd, 1974. However, Easter fell on April 14 in 1974.
The jig playing in the background when Snoopy arrives as the Easter Beagle is the first movement of Beethoven's 7th Symphony in A Major. The second movement from this same symphony is heard when Sally turns impatient about the Easter Beagle's appearance.
Continuity
All the furniture in Woodstock's new birdhouse disappears when Snoopy breaks the birdhouse after his nose gets stuck.
When Snoopy and Sally are trying on hats, a brown hat that Snoopy takes off turns purple when it hits the ground.
As Lucy is putting out the eggs for the Easter egg hunt, all of the eggs in her basket are of solid colors but each one she takes out is elaborately decorated.
When they go to the shopping mall and see all the Christmas decorations, Lucy tells Linus, "I told you this was the gift-getting season!" She did say that earlier, but when she was talking to Schroeder, not Linus.
Factual errors
When the gang visits the mall, a sign proclaims it is 246 days until Christmas. Assuming the film's events take place in the year of its release, this means the date is April 23rd, 1974. Easter fell on April 14th that year, so Sally is searching for Easter shoes 9 days after the holiday.
Miscellaneous
Incorrectly regarded as goof: While Snoopy and the gang are at the mall, the gang takes one escalator up and Snoopy takes the other down. As they do, they cross paths, even though they're going in different directions. This is a visual gag intended to be silly.
Audio/visual unsynchronized
Snoopy's mouth does not move when he shouts, "Hey!" to the dancing bunnies.