'Betty Boop's Hallowe'en Party'
And Toby the Pup 'Halloween'. Wait till about the 3:25 min mark for things to get spookin.
A side note about this one. As far as I know, all Toby the Pup cartoons are public domain. However, not many of them survived. This was posted on Youtube earlier this year from a European source (can't remember where), and then removed a few months ago.
If you enjoy these old cartoons you might also want to check out Uncle John's Crazy Town. His posts are great year round, but right now he's got a few spooky ones up for the month of October.