Honk is a villainous criminal in Jump City. He was originally a clown for hire until he was submerged in Beast Boy and Cyborg's X-treme-ification chamber as part of their efforts to make clowns cool again, genetically modifying him.
The clown was hired to perform at the Teen Titans' victory party after they managed to defeat their arch enemy, Slade. Starfire, suffering from coulrophobia (the irrational fear of clowns), screamed and hid underneath a boulder outside the island. Beast Boy and Cyborg, who had requested the clown to reexperience their childhood love for them, were unsatisfied by the clown's act and decided that they would make him cooler. The clown was forced to sign a waiver that allowed the two Titans to experiment on him, and after perfecting a chemical that transformed a bug into their image, was submerged in an X-treme-ification Chamber. This genetically modified his skin and hair, causing the clown to become evil.
The clown was unveiled to the other Titans and he promptly began beating up Robin. Raven was initially amused, but saw that the modified clown was a perversion of children's entertainment. Beast Boy and Cyborg ignored her warnings as they thought the clown was now as cool as they remembered. They decided that he would spread his coolness on Jump City and handed him a squirt gun filled with the X-treme-ification chemical to accomplish his task. The clown immediately jumped out the window, laughing manically. He planned to transform children's entertainment into darker and scarier versions as the Titans had done to him which Raven discovered upon viewing Pretty Pretty Pegasus.
He eventually made his way to Lil Alfred's Toy Cave and sprayed several toys with the chemical solution, causing them to mutate and terrorize the children. His actions were witnessed through video by Robin, Beast Boy, Cyborg, and Raven, who advised that they defeat him by making him remember the clown he was before the mutation. They dressed up as clowns and flew an airplane to the establishment where the four performed typical clown acts, causing the clown to laugh. As they performed their big finish, the clown stopped laughing and thanked them for the laughs with an evil glare. He leveled the squirt gun at them when he was suddenly knocked unconscious by Starfire.
Before he was a normal human, but to make him "cooler", Beast Boy and Cyborg did evil science and turned him into a mutated murderer freak.
The clown shares similarities to the Joker. They are both humans who were genetically modified and received a different skin color and green hair. They both also used items relating to them as weapons. In the clown's case, he uses children's entertainment while the Joker uses common clown acts.