Continuity mistake: The lampshade by Charlie Brown's bed changes throughout the film. First it's just a blank shade with nothing on it, then near the end of the film it has two boats printed on it. On the boats there are orange flags on top that first face each other, then change suddenly to both facing the same direction.
Continuity mistake: When Linus is in Charlie's bedroom towards the end of the film, you can see there is nothing next to the side of Charlie's bed, but when Linus leaves the room, Charlie's shoes and a sock have appeared.
Continuity mistake: When Linus and Snoopy enter the theatre where the spelling bee is taking place, you can see they are entering from the interior of the building, but when Linus tells the usher he's a friend of one of the contestants, they are shown going inside from the exterior.
Continuity mistake: Lucy gives Snoopy Charlie's red kite and he flies it. After a quick cut to Charlie, we return to Snoopy, and the kite he is flying is now yellow.
Continuity mistake: When Charlie is looking out of the window when he is on the bus with Linus and Snoopy, the bus passes the same garage three times.
Continuity mistake: When Charlie, Linus and Snoopy enter the bus at the Depot, Charlie goes to his seat and you can see he is sitting near the arm rail, but when the bus starts moving he is now sitting near the window.
Continuity mistake: When Charlie, Linus and Snoopy leave the Spelling Bee after Charlie lost, you can see they have nothing on their heads, but before they enter the coach at the Depot, they are all wearing hats.