But what if you're a die-hard member who still hasn't gotten their costume together? Don't worry; Luke, Ashton, Michael and Calum have got you covered.
So if you want to be like Luke and dress up like Michael, it's pretty simple. According to the man himself, all "you need a red wig." Easy enough!
Now, Luke and Calum insisted people wouldn't be dressing up as them for Halloween (which we don't believe), but they were all happy to give out some tips on how to nail Ashton's look, who, at the time, they all wanted to dress up as.
"You need to be very muscular to dress up as Ashton," Michael said before Luke added. "You need a muscle suit and maybe some glasses."
On Friday (October 31) the guys opted to not dress up as each other, but still had some pretty impressive costumes. Ashton had the "weirdest awesomest time" going full-on whoopee cushion while Luke and Calum "dominated the dance floor" as the dynamic duo that is Mario and Luigi.
But it seems like someone may have turned up with the same costume on. Awkward.
No sign of Michael hanging out with his bandmates, but he has a good reason, it seems like he was a bit busy.
That's definitely a Halloween treat no one will forget.