Karkotaka was a naga king, who bit Nala at the request of Indra, transforming Nala into a twisted and ugly shape. Karkotaka had deceived Narada who cursed him due to which he could not move a step. Karkotaka was friend of Nala and suggested Nala to go to Rituparna, king of Ayodhya and stay there under a changed name Bahuka.
It is believed that these were the people who lost maximum heads in war with Yavanas, and hence, later on they were also known as Katewas like Shishodia in Rajputs.
The group of people developed their Vamsha according to their system of worship of Devas and Nāgas. The worshippers of Shesha Naga were known as Sheshama and worshippers of Karka Naga were known as Karkotaka. Thus Karkotaka was a Nagavanshi king. The descendants of Karkotaka are still found in Jats of Rajasthan as Katewa clan.