海绵宝宝笑得没心没肺
[hăi mián băo băo xiào dé méi xīn méi fèi]
This refers to laughing heartily and freely, without a care in the world. SpongeBob (a character from the famous cartoon 'SpongeBob SquarePants') often has a lighthearted attitude which makes this name seem playful and easygoing.