Oooh, it's time for a pop quiz! This one's an essay question!
This official UNDERTALE pen was designed by Laura Verdin and produced in Denmark by none other than the inventors of the floating action pen, Eskesen.
Ohto 705NP refill cartridges work with this pen, once trimmed to fit. Other refill cartridges with similar properties should also work. To refill, pull the pen straight apart from the center seam, grasping both ends and using steady force.