Although this was the last episode broadcast, it was not the actual finale. It was in fact the 19th episode produced, but had been pre-empted by the Super Bowl. By then, the format had been changed to send the astronauts back to the "present." However, instead of airing it the following week, CBS opted to jump to episode #20--the one which returned them to the 20th Century. And so this episode was burned off the week after the actual final episode, with no explanation given as to why the astronauts were still back in prehistoric times. Interestingly, when AntennaTV began rerunning the series in the fall of 2015, they aired the episodes in production order; thus, this episode was correctly shown between #18 and #20.