A personal favorite...
más feliz que un perro con dos colas = happier than a dog with two tails
I particularly like this one. If you don't get it (I didn't) welcome to the dense club. After giving the hubs a blank stare the first time he pulled this one out, I asked for an explanation.
I got the "you-are-so-dense-light-can-not-escape-you" look.