- Enforced Method Acting: If Craig Charles looks genuinely shocked when handed a picture of Kryten's genitalia, it's because he was handed a Polaroid of some actual bloke's penis, which he hadn't been informed was going to happen beforehand.
- Throw It In!: The part where Cat sneezes on the microscope was not originally in the script but was a joke done by Danny John-Jules in rehearsal. The crew liked it so much that it was decided to include it in the episode.
- What Could Have Been: Kryten was to remain human at the end. Unfortunately for Robert Llewellyn (who was looking forward to not having to go through all the makeup), the episode was moved away from its position as the last episode of the season, so he was turned back for continuity.
- Working Title: The episode was also entitled Do Not Alter and DNA: Do Not Alter before being shortened to just DNA.
Trivia / Red Dwarf Season IVDNA