It's the Great Pumpkin, Charlie Brown [1966]

Random Trivia For This Title:

• When Linus walks into the room after writing a letter to the Great Pumpkin, Lucy is sitting in front of the TV reading a TV Guide. The picture on the cover of the magazine is a picture of Lucy.
• When the show ran briefly on NBC, the scene of Snoopy and Schroeder was cut out.
• After this special originally aired, children all over the country sent candy to Charlie Brown out of sympathy.
• When Snoopy pretends to cross wartime France as a downed pilot, he passes signs pointing to two real locations in the Champagne country northeast of Paris, Chalons sur Marne and Pont a Mousson.
• Actress Kathy Steinberg had almost finished recording all her lines of dialog as Sally when the producers received a phone call from Steinberg's mother informing them that one of Kathy's teeth was loose. Fearing that a sudden lisp would ruin the continuity dialogue, the producers rushed the young actress into the studio to finish recording her lines. Just as Steinberg was speaking her last line, the tooth came flying out of her mouth.