So at first I thought it’d be best to put Gon in an outfit like a french maid or whatever, some kind of stereotypical fetish outfit. But then I remembered the Gold Dust Girl, a trading car/video game NPC in the Greed Island arc which is basically the only character Killua shows attraction to in the anime (that I can recall). This joke in the show is probably just based on the fact that her trading card image shows her naked in a tub, but regardless I thought it’d be cute if he projected that interest to Gon by wanting to see him cosplay her. Also it was fun to put Gon’s hair in a different style.