Okay so this is a way to mount inside...
You eat pumpkins untill you get the skeleton outfit. You then get a costume on from the Halloween Wand's... Must be one that's rideable. Then you mount outside, and remove the Wand's Costume, and you will be on your mount as a skeleton.. you will be able to use it inside, but at walkingspeed or 60%, can't really figure out hehe