| Please note the following:
Jeffo was a one-time character that appeared as the main antagonist of Robot Jeffy. Jeffo was a robot replica of Jeffy, built and created by Cody's robot, Codo. Jeffo was built to go to detention for Jeffy since he didn't want to go. Shortly after being built, Jeffo went on a killing spree due to Bully Bill enabling its Kill Mode and vaporized him to ashes, and later tried to kill Mario, Bowser Junior and Cody. It was eventually destroyed by Codo's laser eyes, along with Codo also being destroyed in the explosion.
Jeffo resembles Jeffy except with red metal eyes. It speaks in a monotone voice, speaking every syllable individually. It sounds like Jeffy but with a more labored voice. Unlike Jeffy, it is incapable of cussing: it malfunctioned when he attempted to imitate Jeffy's "are you f**king high?!"
- Jeffo, along with Codo's eyes are from a Funko Nightmare Freddy plush.