These are all good questions. Let's try to sort some of them out. Large pet toy manufacturers have a team of people that design toys. They often have test subjects in their office, adopted rescue pets, maybe they bring their pets to work but the toys they design are pet tested for four paws up approval. The components that go into pet toys are usually standard. Cat toys more often than not contain catnip. Most cats adore catnip, it's a sort of cat pot. Catnip makes kitty feel good, happy and frisky.
The most popular cat toys are mice. Most toy mice contain catnip inside the body of the mouse. Cats have a natural hunting instinct so when a toy mouse is moved, kitty thinks it's the real thing. Most toy mice have a fur type covering, when kitty puts the toy in his/her mouth it feels like a real mouse. Some toy mice are covered with rabbit fur. Oh my gosh, was a rabbit killed to make this toy? Certainly not! Large pet supply manufacturers have agreements with Countries where rabbit is a staple of the human daily diet. The rabbits are grown for human consumption, the fur is sold to manufacturers for many reasons, one of them being cat toys. Rabbit fur even after being processed has a scent that kitty can smell, making the toy even more enjoyable to your cat. Rabbits were not killed just to manufacture a toy mouse.
Some toy mice are covered with faux fur, a soft plush man made material. Cats like things that are soft and pliable. Most toy mice have leather tails. The first thing my cat does with a new toy mouse is eat the tail. The Vet confirmed this would not harm him if he eats a leather tail once in a while. The eyes are often made of felt. Some have beaded eyes and noses that are securely fastened from inside of the mouse. Some toy mice have hard plastic bodies under the fur and some have little rattles inside, others are made with cardboard bodies and do not rattle.
The things that go into cat toys are carefully thought out by pet supply manufacturers. Pet toy manufacturers design toys for pets so they can play safely.