Blooper

When the kids are putting on their Halloween costumes, Charlie Brown's ghost sheet has many holes in it. Shortly after, when Snoopy marches out the front door as the World War I Flying Ace, Charlie Brown holds the door open for him and salutes. When he does so, all the holes in his ghost costume disappear, except the eyes, only to re-appear later.

In the trick-or-treating scene during which Lucy asks for an extra piece of candy for her brother, her right hand has five fingers when she holds it up, but her left hand only has four fingers.

When Sally decides she's going to join Linus in the pumpkin patch instead of trick-or-treating with the others, her ghost costume she was holding vanishes suddenly.

In the opening scene in which Lucy and Linus go out to the pumpkin patch, we see the setting sun in the background, which the children pass as they walk. However, the sun (just like the moon when we drive a car) would not be "passed" as though it were a stationary object; rather it would "move" along with the person moving. A second setting sun appears at the end of the same shot, after the children turn a corner and walk in another direction.

Linus' letter to the Great Pumpkin disappears from his hand in one frame as he takes it to the mailbox.

Just before Snoopy rises in the pumpkin patch Sally is standing with her arms crossed. Her left hand is painted in the same color as her dress - the animators didn't realize it was her hand.

At the Halloween party, Violet says, "Charlie Brown, you'll have to model for us". When she says that, she suddenly grows a third hand, then she has two hands again shortly after.

As Linus carries the giant pumpkin towards the fence with the opening in it, the shot cuts to the other side of the fence. Linus tries to get the pumpkin through the opening, but it's too big. A few seconds later, Linus comes around the far end of the fence. But Linus is not seen through the opening in the fence heading down to the far end of the fence. He could not have gotten there without us seeing him through the fence opening.

When Linus is seen on one side of the gate, the gates have nine planks on the right side of the gap. However, when you see the other side, those same planks are only in a number of seven.

Linus and Sally have the moon behind them in the pumpkin patch while Snoopy has the moon behind him as well. They are facing each other, therefore making it seem as though there are two moons.

When Lucy and Linus are talking at the table, the table bounces and rattles several times.

Modern merchandise designates the character wearing a green mask and a purple hat as Patty, however, this retroactively creates an error due to the character asking "Patty is that you?" during the costume dressing scene. A character wearing a similar blue mask appears in the extended Coca-Cola/Dolly Madison opening and a cel of the scene that circulated online shows the character having hair very similar to Patty's.

Lucy gets disgusted that her "lips touched dog lips", when dogs in fact, don't have lips.

When Lucy goes to the pumpkin patch to retrieve Linus, he's shivering and half asleep with his blanket covering him. When Lucy wakes him up and walks him home, he simply stops shivering when he should've still been doing so until he got into the house.

Sometimes, the trick-or-treaters say they have less candy than you see them get.