Jeff, Karl, and Konor were a trio of weasel henchmen working along side Nack the Weasel when he abducted Sally Acorn. After Sally was successfully knocked out and grabbed by the weasels, Jeff was knocked off his speeder bike and captured for interrogation. Unmoved by Bunnie Rabbot's threat to drop him out of a window, he later was convinced by King Max and a group of his strongest royal guards to reveal the location of Nack, Karl and Konor. (StH: #122)
Nack, Karl and Konor arrived at an old mansion passed on through Nack's family, where they planned to hold Sally hostage and make the Acorn family pay ransom for her return. Sally managed to lure Nack into a false sense of security before knocking him out and making an effort to escape. Karl and Konor gave chase, but before they could shoot her, Sonic the Hedgehog arrived and subdued them. Karl and Konor were later brought back and imprisoned with Jeff, while Nack managed to flee the scene and avoid incarceration altogether. (StH: #123)
Some time later, Nack was imprisoned after his failed assassination attempt on Mina Mongoose. Threatened with being put in the same cell as Jeff, Karl and Konor if he didn't reveal who hired him, Nack squealed on Dr. Eggman. Later when Nack escaped from his cell, he went to the prison kitchen and poisoned the food, which resulted in the death of the three weasels. (StH: #153, #163)
- In StH #163, Nack states he planned to "Hit the kitchen on my way out and leave my former gang buddies a little 'gift'". Because it wasn't specified in the issue clearly, writer Ian Flynn elaborate in a Q&A that Nack poisoned the prison food, thus killing off his cousins. (1)
- Artist Jeff Axer, who designed the trio, named the weasels Karl, Jeff and Connor after staff members who worked on the story in which the weasels were introduced, including Karl Bollers, Jeff Powell and Conor Tomas. The names were never specified in the comics, and were only made canon with the release of the Sonic Encyclopedia.