Apparently, the reason Kris has a sword is because they carry a pencil in the Light World. Items on your person are usually converted into something similar in the Dark World. SO, using this logic, if you were to have a gun (or even just a nerf gun) on your person when entering a Dark World...
Canon Ralsei: Hey Kris, let's try to make it through without hurting anyone if we can! Canon Susie: I like beating people up for fun! Fanon Susie: Guys, I don't think we should hurt people, especially if they didn't do anything wrong! Fanon Ralsei: I love taking advantage of my second amendment rights!