Kunekune (くねくね) is a mysterious, blue lifeform that can freely change its appearance and voice, allowing them to disguise themselves as someone else.
In the past, they used this ability to cause mischief, until a good wizard caught them and trapped them inside of a crystal. Later on, the crystal that they were trapped in, broke open after Karaagemaru threw cat fireworks at it. This allowed them to escape and cause mischief again by disguising themselves as Hideyoshi and then steal and eat three tuna fish from two fish stores. They were eventually caught again by Hideyoshi, Takuma, Tempura, and Pantsu.
Atagoal Monogatari Chapter 18 - Kunekune in the Crystal Box (水晶箱のくねくね)