MayDay: Can you holloween as a stage name? She'd probably go as Kul Fyra if so. Or she splits a costume with zuke
Zuke: probably twinning with May, who ever the percussionist of the goolings was.. or he splits a costume with may
DK West: d.... donkey Kong (I cant think of anything)
DJ Subatomic Supernova: he either just puts on those headphones with the cat ears and calls it good, or goes for some obscure spacey thing. Could also see him going as Carl Sagan gjkfjf "why are you wearing that" "*sputtering* I could not be more OBVIOUS in my costume" "... I'm pretty sure you could"
Sayu: Ariel from little mermaid or the alien girl from BNHA (I dont know her name) [also in a less sexualised outfit]
Sofa, Dodo, Remi, Tila: whatever their current anime interest is. I don't watch enough anime. Could also uh.. go for superheros, justice league style.
Yinu: dorothy from wizard of OZ, her mom is the wicked witch
Neon J: pirate captain hours
1010: pirate crew hours
Eve: something that messes with your mind so much it gives you a headache. Or a statue where she doesnt move for 90% of the night
Tatiana: i can see her being lazy and saying "human torch from fantastic four", and saying she wont do anything more because shes so busy.... and then showing up in a really detailed costume (I have no ideas)