Originally, I was a little put off by the style.
I'm not a huge advocate of "mainstream anime" styled cartoons, unless its something like Hayao Miyazaki, Satoshi Kon, etc. Aka, quality animation.
the story of your animation really pulled me in.
At first, I was a little skeptical as to what was going to happen, but it was done nicely. And I think adding Jack giving the little girl candy at the end, was a great touch... shows that he only shows malevolence towards those who ruin the Halloween spirit. Halloween is all about trick-or-treatin' yo!
Regardless, I was quick to get over my gripe about the style, and the, no offense, but poor and somewhat unbelievable script that the characters shared with each other.
I mean, them waltzing into a creepy person's house and Vince's urge to stay didn't quite make sense to me. But regardless, it was good.
If you ARE looking for improvement, and this is just my input:
Make them more of downers on the halloween spirit... like do more than just scare kids and take candy. The witch girl could totally be a whore too... like, she just wants to go to the party to get with cute guys there and hates trick-or-treating or even little kids. Vince and Dugg could totally TP and throw eggs at people's houses and do more crazy things. Maybe Dugg could take candy from little kids by force. If the characters are assholes, we feel a bit more relieved when they get turned into candy. I also felt putting their faces at the end in the candy was unnecessary... leave their fate extremely subtle. Or if anything, have them shake slightly. Candle thing was pretty awesome too.
On a personal note, I felt that the scares and their fates could have been creepier, too. Hands down, the witch girl's little trip was the best, but I didn't feel like her fate was really justified; she wanted to avoid trouble and just go to a party, nothing really wrong with that.
Vince and Dugg sorta of deserved it, but even then, not really... so then it really brings into the question of just how justified is Jack, the spirit of Halloween? Making them bad and extending their trials would be awesome, like all three sort of explore the different parts of the house or something... and meet their creepy end.
Holistically, this was good. I enjoyed it, and the ending was done well, just don't add the whole "help us! save us!" bit at the end.