Help me decide the guest character!

Hello everyone! I would like to ask your help deciding the guest character for next, halloween-themed, picture set :D

Who will join snooping elf Serena in her spooky adventures? ;) I've selected some characters who could fit the set, so you can help me decide who will be the guest star this time :) In the meanwhile I'll keep working on the new set so to have everything ready for when time comes to post the full thing :D

Attached is a teaser for next set and the list of characters for the poll :)

Thanks a lot for your help!