The esteemed committee who decides such things (i.e., Gustavo and me) chose "Possession" from Beast Wars as the October episode. Waspinator gets possessed by the ghost of Starscream! Oooh, spooky!
For those who don't own the episode on DVD, here's a site where the episode can be found:
http://tinyurl.com/bw-possession
Zob (twinkle, twinkle, little Starscream)