Votre enfant est gentil à croquer = Your child is a charming little fellow.

Il croquait le marmot = He was dancing attendance; He was cooling his heels.

[Littré gives as the explanation of this obscure expression that artists while waiting for their patrons used to draw pictures of little monkeys (marmot ) in the vestibule. Others assert that in the antechambers of the rich were to be found dishes of cakes in the form of little monkeys, which visitors used to eat (croquer ) whilst waiting. But both explanations need confirmation.]