Speaking of The Snake and the Crab in Ancient Greece was the equivalent of the modern idiom, 'Pot calling the kettle black'. A fable attributed to Aesop was eventually created about the two creatures and later still yet another fable concerning a crab and its offspring was developed to make the same point.

The crab spoke thus,

seizing the snake in its claws,
'One’s comrade should be straight
and not think crooked thoughts.’