The stage setup was really neat too, it added a lot to the experience. everything was painted white (even the cymbals) and big light-up squares were hung from the ceiling. Trey played a Strat instead of his signature Languedoc which was neat. Trey and Mike had little choreographed dance routines made for a bunch of the songs. Definitely watch the video of it if you can. I'm sure it will be popping up in various places. there are some pics in the jambase article that pitchfork links: https://www.jambase.com/article/phish-halloween-2018-setlist-recap
It was kind of like they were doing a Dukes Of Stratosphear type of thing. Taking on a new wave band (I guess? some are calling it "prog" but it's definitely not prog) as their alter ego. It seems obvious to me that they wrote all these songs with the intention of them fitting into the concept rather than repurposing whatever new songs they had lying around.
They had tried the "premiere new material for Halloween" trick twice before. first in 2013 with "Wingsuit" which was a fine show but was kind of a disappointment too since they didn't do anything more than "here are a bunch of new songs" and they were clearly still working on some of them so it was a bit underwhelming, and while the album that resulted from it (2014's Fuego) was a fine record with it's share of highlights ultimately it was just a typical phish album. Then in 2014 they did it again with "Chilling Thrilling Sounds of the Haunted House" which was a sound effects album that Phish wrote instrumental backing for. A fun idea that was perfectly suited to a halloween-themed show, and several of those songs have entered regular rotation for the band, but the songs were basically glorified jams so while they work great in the context of a show the songs don't really work on their own. This new Halloween took the premise all the way with completely new songs all of which fit into the silly concept, but also sound like fully fledged songs which can have a life beyond this Halloween show. All in all an inspired way to debut new material.