Andrew Denton says he's an introvert trapped in an extrovert's career.He's been one of Australia's most creative forces - as a radio and TV comedian, a Walkley-winning interviewer and a producer of hit shows like 'Gruen', 'Hungry Beast' and 'The Chaser'.But witnessing the painful death of his own father led him to the work that may have had the biggest impact - as a tireless advocate for end-of-life choice.