|Josh and Zack Greenfield|
|Family||Each other (Brothers)|
|Played By||Diego Klattenhoff (Josh) and Nolan Gerard Funk (Zack)|
Lionel Luthor started a program to mix kryptonite with steroids to create super-powered dogs; however the results were only temporary. Josh was a trainer at LuthorCorp and stole their research. He used it to enhance two dogs from the animal shelter in which he and his younger brother work:
- Einstein is a golden retriever. He was bred to have super intelligence and strength, and was smart enough to open safes. Einstein ran away from the Greenfield brothers and was hit by a car by Lois Lane. He was taken in by the Kents and renamed Shelby.
- Hercules is a large black Rottweiler. He was trained to steal and attack, using super strength. He was strong enough to dent a steel door, and badly injured a grocer. He ran away and bit Jonathan Kent in the arm. When he was recaptured by the Greenfield brothers, they attempted to destroy him along with their getaway truck, but he was saved by Clark and Einstein.
These brothers trained the dogs to attack and be smart enough to steal for them. They prepared for a heist and unleashed the two dogs onto a convenience store. When Clark Kent got into the van and was exposed to kryptonite, the brothers found him in the back and prepared to set the van on fire. Einstein managed to save Clark and got him away from the kryptonite. Clark then knocked the Greenfields out, and they were sent to jail.