(it's not Halloween since it already passed but I was bored and made this and there's no gyomei)

Sanemi: didn't dress up because he found it childish

Giyuu: mitsuri braided Giyuus hair to make him look like Wednesday Adams

Obanai: mitsuri forced obanai to dress up as a cat

Muichiro: mitsuri also braided his hair

Mitsuri: dressed up as a princess

Rengoku & tengen: they got face paint to make him look like a skeleton

Shinobu: dressed up as a witch