The term 'Stubborn Critter' can be broken down into two crossword solutions: ASS and MULE. An ASS is a hoofed mammal of the horse family, known for its stubbornness and intelligence. A MULE is a hybrid animal, created by breeding a male donkey with a female horse, also known for its stubbornness and strength. Both animals are often used as beasts of burden, and are known for their hardworking nature and refusal to give up.