In October 1966, [Ray] Bradbury and his daughters sat down together to watch [the first airing of] the Halloween special It’s the Great Pumpkin, Charlie Brown and none of them liked it. They were all disappointed that The Great Pumpkin didn’t show up and felt it wasn’t a proper Halloween film at all. Bradbury complained about it over lunch to his friend, animator Chuck Jones, who agreed with him.
https://www.mouseplanet.com/12510/Three_Disney_Halloween_Treats
Ray Bradbury is one of my all-time favorite writers, but I disagree 100% with his reported opinion of It’s the Great Pumpkin, Charlie Brown, which was written by one of his cartoonist friends named Charles M. I’m not really surprised that the other Charles M. didn’t care for it but, in my opinion, It’s the Great Pumpkin, Charlie Brown is the best of all animated TV specials.