Is it normal for 3 3/4ths year olds to act insane and irrational?

It sounds like at home he is not having any boundries. Children need structure. They need a clear understanding of what is right and what is wrong, and if they do something that is wrong they need to know that they will be punished for it in some way. Again, this should be consistant. I dont understand these parents that think children should just be allowed to run free and basically run the house. My son is 4 and is SO well behaved. We get compliments on him all the time. I have never ever ed him either. He just has a clear understanding of what is right and what is wrong. He knows if he acts up he will be punished. Timeout did not work for him, so we started taking away something he liked...mostly tv. He knows if he misbehaves he does not get to watch his favorite program. Its going to be hard for you to have him behave if his parents let him run free and throw rocks, hitting other kids and everything, but at least if you are teaching him right from wrong he may learn to act correctly at your house at least.