Appearance and effects
The invention was modeled from a water pistol for easier portability. As the pistol had no room for a dial, the Transmogrifier Gun was designed to work on telepathy, so that the user could simply point the gun and set it off on his target. The gun would read the mind of the user and the target would then be turned into whatever the user was thinking about. The gun has been known to malfunction from excessive usage. Also, its effects are temporary; one of Calvin's transmogrifications wore off within a day.
In between its appearances, the gun's color scheme changed; from its original pale blue (represented as black in the uncolored strips), it subsequently became white later on. Calvin must either have repainted it, or made a new gun entirely. As the Transmogrifier Gun had previously malfunctioned, both hypotheses are equally valid.
The Transmogrifier Gun first appeared in the 2/8 through 2/20 1988 story arc. Calvin designed the gun in secret over the course of a morning, and only unveiled it to Hobbes after it had been completed. He then gave him the gun and asked Hobbes to transmogrify him into a pterodactyl. However, Hobbes failed to comply, and turned Calvin into a chicken (as he was thinking about lunch). Hobbes then did turn Calvin into a pterodactyl - albeit a tiny one, which infuriated Calvin. Conflict ensued with both parties transmogrifying back and forth until finally Hobbes was in his normal form and Calvin had turned into an owl. The gun had malfunctioned after Hobbes' restoration, and Calvin was unable to change back; however, the effects of the transmogrifier unexpectedly turned out to be temporary, and Calvin was back in normal form the next day.
The Transmogrifier gun made one more, far briefer appearance. In the 7/4 through 7/15 1988 story arc, Calvin floated into the sky on a balloon, and undertook a long free-fall after it popped. He was saved, however, by his Transmogrifier Gun, which happened to be in his pocket at the time. The gun had a different color scheme in this story arc; since it had previously malfunctioned, it is possible that this was a new model.