Theobromine is your search term if your poochie has got some chocolate, it causes some UGLY poos in my dog, who has stolen the odd illicit bit, and according to the vet. lit. it can cause all sorts of problems, some of which you can reverse if they show symptoms... others may get away lightly - just like with humans and drugs. Worth a google though, and also avoid raisins and onions with dogs, look it up, know your enemy!