There are undoubtedly plenty of extroverted people that look introverted. Though chances are, if you talk to them for a bit, they'll find a way to let you know that they're extroverted. Extroverts are too outgoing and energetic to conceal their personality for long, they're inherently social people and want you to know it. Even if they don't directly inform you, they'll show themselves with a combination of behaviours, beliefs and actions - traits you should recognise in people of any background.