I also watched YOU'RE NOT ELECTED, CHARLIE BROWN which is also on the GREAT PUMPKIN disc. (It was also shown tonight on ABC). Might not on the surface seem to have anything to do with Halloween, but Linus is running for class president, and during his campaign, he happens to mention his devotion to the Great Pumpkin which almost costs him the election.
This was made in 1972, so it's not the classic that those 60s Peanuts cartoons are. Still, it had a few entertaining moments.