Insanity is technically the state of being mentally ill, it is also known as being batshit, clownshit, or in the case of temporary insanity, going apeshit.
Insanity comes in many forms; some are hilarious, others are sad, still more are scary. Below are some of the more notable types.
This is what most of us think of when we hear "crazy". Schizophrenics have a "distorted view of reality". In other words, these are the people who could see you as the last unicorn and dedicate their lives to protecting you, or could carve your eyes out because they are bug-headed demons telling them to eat shit.
The 80s brought us a wonderful RPG based on a horrible mental condition
An irrational fear that someone or something is out to get you. Paranoia can often result in you yelling at people for walking behind you (WHY ARE YOU FOLLOWING ME?!?!) and questioning people about their involvement in conspiracies that probably only exist in your head. Probably.
Andrew McCarthy (He was the Red Crisis guy, right)
It is not okay to like Buffy this much.
Obsessive people focus on one thing and can't let it go. Stalkers are obsessive. The average Cracked writer's fixation on large breasts is obsessive. Obsessions can be fun, as long as you indugle them in the privacy of your own home and they don't involve things like screwing animals or stuffing marshmallows into dead people's orifices.
Obsessive Compulsive Disorder is different from straight obsessive types. You don't really need to worry about OCD people doing much more than annoying you (or entertaining you like that card Monk. Good times...) You average OCD sufferer has rituals that MUST be gone through in order to continue in life. They won't kill you because they would then have to count all of the blood spatter, or they might get it on their immacualtely clean clothes. (22.214.171.124,126.96.36.199. "How many pieces do you wish?" Phew... That's better)
Hobo crazy is a mixed bag of other insanities. In this case, the bag is filled with spiders and rotten banana peels and you are lilkely to pull your hand out with an infection that smells like pee and old pizza.
Cat Lady Crazy
Cat lady crazy is an offshoot of Hobo Crazy that involves some OCD. It involves a lot of screaming and feelings of persecution, plus cats. Lots of cats. You know that grab bag of hobo-crazy? This one has angry felines and smells of unchanged litter boxes.
The Cat Lady from the Simpsons