Kat and Jesse built in a small air compressor to activate the "glitter sneeze." It runs through a gravity-fed glitter containment unit, and is controlled from an arduino switch that is activated by a button on the base of the sculpture.
Beverages are run by a CO2 pressurized corny keg, also in the base, with a beverage tap at the crotch. She was originally supposed to pee champagne, but Vermont liquor laws prohibit anyone who is not a licensed bartender from serving alcohol on public land, and we weren't able to get the unicorn licensed in time. Plus, we figured that with lemonade, the kids could also partake -- and have something to talk about with their therapists later.
Katy Perry's horn is hammered copper with a flame-cut finial. The fire effect is an aerosolized methanol spray (which creates the pink color and liquid-looking flare), with a propane pilot.
Under supervision, wedding guests could activate the flare via a button on the back of the base. When timed correctly, she shot fire and sneezed glitter at the same time.
She sneezes glitter, pees lemonade, and shoots pink fire.