Question: what are all the office halloween episodes?
Answer: Season 2, Episode 5 - "Halloween" ...  Season 5, Episode 6 - "Employee Transfer" ...  Season 6, Episode 8 - "Koi Pond" ...  Season 7, Episode 6 - "Costume Contest" ...  Season 8, Episode 5 - "Spooked" ...  Season 9, Episode 5 - "Here Comes Treble"