 The references in "Unending" to the events of season 2's "The Fifth Race", another Cooper-penned episode often named as a fan favorite, were intended, as were the callbacks to season 9's "The Ties That Bind" (the Daniel-Vala argument, see below) and season 10's "Line In The Sand" (the solution of using the Ori beam).The period aboard the ship was originally significantly less than fifty years, but the actors' last-stage makeup, which Cooper only saw minutes before filming, looked so old that Cooper was forced to increase the number of years in the script.Cooper originally wrote the developing romance between Daniel and Vala in "Unending" by having them have sex without a confrontation.