Coco (the clown) could be considered a fool and (Our) Lassie was a famous racehorse from the early 1900s.
Perhaps that’s a stretch, so merely a suggestion.
I can accept Coco for fool, but Lassie for horse on the basis of one over a century ago which wasn’t even called Lassie but Our Lassie is far beyond a stretch. Lassie was a dog. Dessie may be what was intended if that is the answer.