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On two separate occasions, Calvin has made duplicates of himself.

First Use: Calvins #2-6[]

In the arc running from January 8 - February 1, 1990, the Duplicator made its first appearance. With it, Calvin created a duplicate of himself, which in turn created four more Calvins. These dupes caused trouble not only for Calvin and Hobbes, but for his parents, Susie Derkins, and even the school's staff. Eventually, Calvin turned the box on its side, converting it into the Transmogrifier. They became worms and were promptly buried in the backyard.

Second Use: Calvin's Good Side[]

The Duplicator made its second and final appearance in the arc running from March 18 - April 3, 1991. This time, an Ethicator was added to the machine, and Calvin used it to make a physical manifestation of his good side. This version also comes with a Moral Compromise Spectral Release Phantasmatron, which was used when the good side threatened a fight with Calvin.