Hi Edna,  it's anatomically impossible for most animals to "laugh" because they don't have the needed motor nerves to move their facial muscles the way humans do. A laughing dog or a smiling horse that we are so used to seeing in the bande dessinée or anime are obviously not scientific illustrations. Dogs and horses can't smile, or laugh, or frown ... at least not on face, whether or not they do so in heart is another matter.

As for a sense of humor, we would all hesitate to accept a speculation as an answer, no? It could be so much fun to set out to do the verification,  but how to design such an experiment? I don't see an easy way, and you? 

Do you think animals enjoy music? Or paintings? Or do they react at all? In dressage, horses appear to be dancing with the music, but we never saw a horse do so without a rider ...

Here is for example a story.
I grew up with a dog, a (few) cats and a parrott from the kind that is called in French cendré à la queue rouge (grey with a red tail). The parrott clearly liked to talk a lot and repeat the laughter of family members, mostly of my mother but sometimes my father's too, and sometimes it was another kind of giggly noise which I thought could be his own after being satisfied of his performance and seeing he's made us all laugh.

The other thing I remember is him showing a more subtle sense of humor and playing tricks on his fellow animal companions. He would call the dog " Johnny, come here" in my mother's voice, and as soon as the dog was facing him he would call angrily in my father's voice "go away!"