Duplication (cloning) – The creation of a duplicate using cloning.
In the Silver Age duplicates were almost always the product of radiation. For example, Red Kryptonite was used to make duplicates of Superman again and again in the Silver Age. In the Modern Age of comic books cloning has replaced radiation as the fictional device to create duplicates. There clones discussed below have been important ongoing characters rather than one-shot plot devices.
Bentley-23 (Marvel) is the Wizard’s clone. 23 is a number that often has numerological significance in fiction. In Fantastic Four V1 #570, the reader discovers that the Wizard is not a very good father to his clone!
Doomsboy (DC) is a clone of Doomsday and made his first major appearance in Superboy V4 #99.
The Guardian (DC) reacts badly when he finds he has been cloned in Superman: New Krypton TPB V1.
Joseph Gardner (DC) is Guy Gardner’s clone and makes his first major appearance in Guy Gardner #13.
The Stepford Cuckoos (DC) are clones of Emma Frost and learned their origins in X-Men: Phoenix Warsong #3.
Xraven (Marvel) is a clone of Kraven the Hunter and first appears in X-Men Spider-Man #4.
The Clone Saga (Marvel) includes a confusing variety of Spider-Man clones and even had a clone of Gwen Stacy running around and destroying the dramatic impact of one of the most important comic book deaths.