Some pets chew grass when they are ill, knowing that it will make them vomit and they will be able to make themselves feel better. Other pets chew grass out of boredom or missing nutrients in their diet. Eating grass is not harmful and no cause for alarm. If you have a cat, you already know that cats love to rub themselves up against your leg, the sides of furniture and walls. As much as you'd like to believe that your cat rubs up against you as a sign of affection, that's usually not the case.
Cats have sebaceous glands in their cheeks, chin and the base of their tale.
By using those areas to rub up against you or someone else, they are in a sense, leaving their mark on you. They could be sitting still one moment and dashing through the room at record speeds the next. This is just your pet's way of being playful. Veterinarians encourage you not to scold your animals for having a sudden burst of energy, but rather, feel thankful. Still don't understand it.