Cats learn how to behave from their upbringing, particularly the lessons they're taught as kittens. If you don't raise your kitten with discipline, he can grow up with behavioral problems. Of course, even a kitten raised with rules can develop behavior problems, so don't blame yourself if he picks up a bad habit here and there -- it's your responsibility, however, to correct them.
Kittens love to play, and they play rough. When they're little, their tiny teeth and feisty attitudes may be more cute than painful, but if you encourage rough play, they grow up thinking it's acceptable. When a kitten uses his claws or teeth on you during play, you must discourage the behavior by ending playtime. Otherwise, he'll keep on acting aggressively as he gets bigger and tougher.
More than half of all house cats are overweight or obese, and it can lead to serious health problems like joint pain and diabetes. Overeating isn't necessarily his fault -- he doesn't know that he has to watch his weight. Overfeeding your cat is easy to do, especially when he's a kitten with a major appetite. You shouldn't necessarily trust him to police his own diet, though, so measure his food out every day according to your veterinarian's advice. If your cat overeats while he's young, working off the weight can take a long time -- it's not like you can take him to the gym.
Even well-trained kittens and cats can develop litter box problems, so if yours develops a litter-related behavioral issue, try to figure out what could have motivated it. For example, perhaps the box isn't emptied often enough, or you recently switched to a new brand of litter that he doesn't like. If you've recently moved the box or introduced a new pet to the home, his behavior could change out of fear, anxiety or aggression.
Cats in the wild eat plants, and domestic cats are no different -- their plants just grow in pots. If your cat or kitten chows down on houseplants, it isn't a behavioral problem, but rather a response to dietary needs. Plants are high in fiber, and they may even help your cat cope with hairballs. The best thing you can do is give him a cat-friendly alternative, like wheat grass, while using deterrents like mothballs or bitter spray on the plants he normally targets.