When Charlie Brown consults Lucy for psychiatric help, her sign (as read from the front) says, "The Doctor Is Real In." However, when seen from the side angle, the sign simply says, "The Doctor Is In."
The number of branches and needles on the tree that Charlie Brown picks out changes from scene to scene.
When Linus is making his speech Charlie Brown is behind him and to his left, and he has is not wearing his red coat. When Linus is briefly shown from his right Charlie Brown is in the background wearing his coat. When the shot cuts back to a front view the coat is off again.
After Linus makes his speech, he walks up to Charlie Brown and convinces him that what he said is what Christmas is all about. After that, Charlie Brown picks up the tree and starts walking out. However, when he walks past the other kids, Linus is within the crowd, despite the fact that he wasn't supposed to be there.
When Linus is giving his speech and the camera draws back for a panoramic shot, there is no yellow Director's Chair on the stage. However, after Linus gives his speech and Charlie Brown exits stage left you see the Director's Chair sitting in front of the left front curtain.
When Schroeder is playing his piano and Snoopy comes on screen to dance, he appears to suddenly appear in the middle of the frame out of thin air. However, dust clouds can be seen on the left side of the screen for several frames beforehand, indicating that this is where Snoopy appeared from.
During the final scene, the Peanuts gang gathers around the little tree and begins to sing "Hark the Herald Angels Sing" (singing "Loo loo loo"). As everyone takes a breath, Pig Pen's head disappears briefly and Patty's orange dress (she's behind him) "pops up" to where his head used to be. Older VHS tapes have the mistake, newer tapes and DVD do not.
The cels of Lucy in her psychiatry stand are not properly aligned to the background, so that the cutoff line of her body overlaps the edge of the tabletop.
During the final scene, the gang is singing "Hark the Herald Angels Sing." Shermy, the boy in the yellow on the right side of the screen, disappears after the gang greets Charlie Brown. In Shermy's place is 555 95472 or 5 for short, the boy in a blue coat who is still on the right side of the screen. So Shermy disappears and out comes a clone of 5 or his coat changed color.
When Schroeder and Lucy are discussing what Beethoven contributed, he stops playing the piano, but the piano doesn't stop right away.
When Charlie Brown and Linus go looking for a Christmas tree, Linus taps on a metal tree and says "This one really brings Christmas close to a person". The tree makes a sound the second before he taps on it, not when he taps on it.
While at her psychiatry stand and naming Charlie Brown's possible phobias, Lucy says, "How about cats? If you're afraid of cats, you have ailurophasia." If Charlie Brown were indeed afraid of cats, he would have ailuroPHOBIA. Ailurophasia is, literally, "speaking cat." She also mispronounces gephyrophobia, the fear of crossing bridges, as "gephyrobia."