Kryten then later reveals to Lister the contents of the secret file the simulant revealed to him: the entire 4000 series of mechanoids was a spiteful joke by their creator, Professor Mamet. They were designed to be a parody of a fiancé who jilted her, and as such were made pompous, ridiculous looking, and overbearing. Further, all their negative emotions are stored on a "nega-drive" and when it becomes full they literally blow up. After Kryten is also made aware of the secret by the simulant, he starts to spiral into a similar depression that caused Able to turn to otrazone, although Lister comforts him by claiming that he has evolved beyond his original personality.