Why do so many singers adopt a second persona, either onstage or in real life? It could be they just can't cope with being their usual selves sometimes -- or, more likely, it's that they're overflowing with more talent than it's fair for just one individual to possess.

Beyoncé aka Sasha Fierce

Beyoncé's new double album, 'I Am ... Sasha Fierce,' is the work of two artists. On one side, the refined megastar we all know simply as Beyoncé. On the other, a brash, sexy newcomer named, you guessed it, Sasha Fierce. Surprise -- they're the same person! As Beyoncé puts it, "Sasha Fierce is the fun, more sensual, more aggressive, more outspoken, more glamorous side that comes out ... when I'm on the stage." Watch Beyonce on Sessions.