Happy as a clam?

Do clams have the ability to experience happiness? I'm thinking no. So why the phrase, Happy as a clam? Is it a joke on the clam, ha ha clam, you'll never know what I'm talking about. Or is it a joke on the person, They're as happy as a clam, meaning they're not actually happy.
stupid phrase, strike it from our brains.



I know I've been as happy as a clam all week. haha
need to pack. off to california again. bummmmmmer!