Inspired by the atrocities committed by Unit 731 , a Japanese research program during World War II , " Nisei " was originally intended to be a stand-alone mythology episode , but was lengthened into two separate parts . The episode featured several scenes that required stunt work , which David Duchovny performed himself . The episode 's title refers to the term '' nisei '' , meaning the son or daughter of an '' Issei '' couple born outside Japan
Unit 731
Unit 731
Nisei (The X-Files)