Story of King Nriga who had turned into a chameleon and later rescued by Sri Krishna is found in the Srimad Bhagavat Purana. One day while the Yadava boys were playing in a large ground in Dwarka.
The boys tried to lift it up with the help of ropes but were unsuccessful in their repeated attempts.
The news of the strange creature in the well reached the ears of Krishna. He came to the well and extended his bare hand towards the trapped chameleon.
In an attempt to catch hold of the saving hand of Sri Krishna, the chameleon lifted his forearms and it touched the hand of Krishna. Then a miracle happened. The chameleon dropped its body and assumed the form of a celestial being.
The chameleon was actually a king once upon a time. He was cursed to be born as a chameleon as a result of taking back the wealth he had donated.
The king thanked Krishna for giving him moksha and disappeared from the well.