Do You Have An Alter Ego?

The success of Beyonce's "Sasha Fierce" album brings to mind the question of alter egos.
Do you have an alter ego, a side of you that allows yourself to do things you normally wouldn't do?
Many people use alcohol or other drugs to become less inhibited and, loosen up, when they are socializing. Others simply tap into a dormant side of themselves, a side that few people get to see, when they want to.
Is it beneficial to do so? I've long ago thought that some people have split personalities, but there seems to be benefits to becoming "another person" when the time is right.
What about you? Do you have an alter ego?