The term THEY MIGHT DOG A DOG can be solved by the crossword solution FLEAS, which is a five letter word. Fleas are small, wingless insects that feed on the blood of mammals and birds. They are known to be parasites that can cause skin irritation and other health problems in both animals and humans. Fleas are often found on dogs, and they can be difficult to get rid of once they have infested an animal or home.