A small amount of chocolate can make a dog sick though is usually not fatal. But the darker the chocoalte, the more toxic. Baking chocolate is the most toxic. Fudge has almost as much butter and sugar in it as chocolate so hopefully he'll have nothing more than an upset tummy. I'd call your vet right away, just to let them know. He might prescribe an emetic (something to make him upchuck) It sounds like the piece was small so he'll probably be just fine but being a little guy, you don't want to take chances. Please check back with us! {{{HIGS}}}