Are you parenting a disobedient 3-year-old? If you are, what you have to know first is that a defiant behavior is fully normal at this age. If this was not the case, something might be wrong. 2-year-olds, for their part, are intense and quick to please their parents because they still don't feel like independent persons. For example, if dad begins to make pancakes, the 2-year-old wants to make pancakes too. And if mom wears a hat, the 2-year-old wants to put on the same hat. But 3-year-olds are very different. Their will to be like mom or dad fades and they begin to have their own opinions and intentions.
3-year-old toddlers realize that they are not an extension of their parents and tend more and more often to assert that. They have their own ideas and intend to apply them their way. They want to be the boss. This kind of attitude is not a problem of misbehavior, this is simply how young children's development works. First, they are unaware of themselves as individuals; then, they become completely centered on themselves, their own emotions being suddenly the only ones that matter. A bit later, as the kids mature, they will be able to shift their focus outward, learn empathy and understand that others may have different feelings than themselves.
In summary, 3-year-olds don't care about tidying up their toys and don't like to be bossed around. For them, it's not a big problem if all their toys remain on the floor forever. Trying to discipline them, telling them about all the importance of cleaning up, or putting them into timeouts, none of that will really work.
So, what should you do instead? Here are some useful answers.
Portrait of a Child by John Singer Sargent (Wikimedia Commons - w/Effects)