This non-Enneagram related page describes the type 3 person really well.
"Perpetrators are notorious for developing an effective plastic, superficial personality. They are charming, engaging and willing to go to any extreme to gain the persons trust. The classic stereotype of the plastic personality is the car salesman. Stereotypes are usually unfair, however are based in a grain of truth. We have all seen the plastic personality type. We have them at our employment, in our families and with our neighbors. Individuals have lost the ability to be REAL. In order to be real and authentic you have to be comfortable in your own skin and you must have some knowledge of who the hell you are as a person..."