This is the alter ego that he becomes every time he wishes to be in the comic book universe of the Crimson Chin. Cleft is also the Crimson Chin's sidekick. He is a parody of DC Comics character Robin from Batman. He himself has sidekicks in the form of The Chin-Hounds, the Chincinnati alter egos of his three fairies.
His look is quite similar to that of Timmy with a few differences. He wears a red-colored costume with a letter-"C" emblem in addition to a yellow cape, gloves, boots, and utility belt (rarely used). He also wears a "utility cleft", a faux chin with various devices used to assist him. He also wears a black mask and a red version of Timmy's pink hat. His identity was set up to identify his alter-ego Timmy Turner more clearly.
Some notable differences in costume design over the series are listed below:
In both Catman Meets The Crimson Chin and Chindred Spirits, his look would be overhauled. There would be more shadows added to the look, and the tights would have black briefs. Also, the cape's interior would be black as well.
His first official appearance was in "Chin Up". When the Crimson Chin loses his fighting spirit and needed a sidekick to help convince him to fight for justice again, Timmy becomes Cleft. He defeats Spatula Woman and tries to get the Chin to rescue the Mayor, but he refuses due to him finding out he was just a comic book character.
Although the Chin is hesitant at first to help, Cleft rushes into battle and gets him put in danger. Cleft reminds the Crimson Chin about Eddie the Imaginary Gerbil and this is enough to restore the Chin's confidence. He then rescues Cleft, before handily defeating the Bronze Kneecap who had taken Timmy and the Mayor of Chincinnati hostage.
Devices in his Utility Cleft
Several of the devices that appear from out of Cleft's chin strap are: