The three Mutant Shredder Clones were a group of entities that lived in Foot ClanHeadquarters and are villains in Teenage Mutant Ninja Turtles. Although their exact origins are still a mystery, it is obvious that they are hideously mutated ninjas that wear armor similar to The Shredder. The Shredder Clones consist of a large, four-armed Shredder (known as Multi-Arm Shredder in toy form, and Shiva Shredder on 4Kids' website), one with large, monstrous crustacean-like claws (known as Claw Shredder in toy form, and Spike-Armed Shredder on 4Kids' website), and a diminutive Shredder with a single, long wrist blade on each arm (called Mini Shredder on 4Kids' website).
In the Mirage Comics the Shredder Clones first appeared near the end of Teenage Mutant Ninja Turtles #20, Return to New York, Book Two. They murder the Triceraton soldier Zog as he is walking through the entrance to their abode. The Turtles battle them in the next issue. During the brawl, the four-armed Shredder clone loses an arm, which to the Turtles' surprise, seems to be exuding earthworms.
The Shredder later elaborates briefly on the Shredder Clones' origin: using a blend of ancient magic and modern science, the Foot Clan's scientists have trained a species of colony worms to feed on the remains of a person and form together to become a replica of said person. Shredder goes on to indicate that the Shredder Elite were experimental subjects and on the fourth instance, they were fed Oroku Saki's charred remains. However, nothing is revealed of whose remains the worms were fed to create the clones nor is it mentioned why they have donned the Shredder's outfit.
The old official website for the series, ninjaturtles.com, and it's later incarnation at miragepublishing.com, referred the three as the Shredder Elite, a name that was sometimes shared with the Foot Elite. For years, this was the only official name for the Mirage incarnation of this collective.
"As far as I recall, everyone at Mirage, including Peter and Kevin, referred to them as Shredder’s Elite back in the day, which is why I did so on ninjaturtles.com."
— Dan Berger
Berger later amended his statement with confirmation from Peter Laird:
"I was, indeed, wrong about them being called Shredder’s Elite Guard - although I talked to Jim Lawson and he remembered it the same way as I did, but Peter has a different memory - and he’s the boss! :)"
Laird alluded to no actual name for the group until the term "Shredder Clones" was being thrown around during the development of the 4Kids series. He also made it clear that unless the clones were fed the remains of the Foot Elite, they had no connection with those characters.
"The Shredder Elite (a name Kevin Eastman came up with, I believe) were the "personal guard" of the Shredder -- Foot soldiers who were more highly skilled in martial arts than the typical Foot soldiers, and more fanatically dedicated to serving the Shredder. They wore those "pancake" hats and had slightly different ninja wear and gear overall.
The three monstrous "Shredder clones" were NOT, as far as I can recall, members of the "Shredder Elite". They were failed experiments created during the period when the Foot were trying to resurrect Oroku Saki using the "colony worms". We never delved very deeply into what they were or what characteristics they had. Were they intelligent? Could they speak? Did they have names? Where did their genetic material come from? Who knows?
Now, is it possible that in these experiments the "colony worms" fed on members of the Shredder's Elite Guard, with the result being the "Shredder Clones"? I suppose so, but it is arguable that these Elite guys were too valuable for such a use, and the Foot scientists may have used others to serve as the fodder for these experiments.
I'm not sure when those three monstrous Shredder-esque beings began being called "Shredder clones", though I have a vague memory that it was a term used during the development of the 4Kids animated series' adaptation of those stories. Given the pseudoscientific explanation Kevin and I came up with for the resurrection of the Shredder (the "colony worms"), it may not be the most appropriate term. But it seems to be the one that stuck."