The BBC's popular TV series Planet Earth may have turned polar bears and piranhas into celebrities, but eight years ago, a different "Planet Earth" brought a star to the Oval Office.

Of all the celebrities who have joined the race to support global warming, Leonardo DiCaprio has perhaps gotten the furthest. For ABC's April 2000 Earth Day special Planet Earth 2000, the Titanic star interviewed President Clinton [transcript] on climate change, energy research, and environmental awareness. But because of DiCaprio's lack of journalistic credentials, the friendly sit-down exchange, meant to boost the image of both the environment and the White House, quickly morphed into a controversial standoff between ABC and presidential officials, with neither wanting to take credit for planning the interview between a movie idol and the President.

From Reagan's career as an actor to JFK's birthday serenade from Marilyn Monroe, the line between president and celebrity is often tricky to navigate. But for Clinton, the importance of the issue clearly outweighed any controversy over DiCaprio's heartthrob status: "I think it's important that programs like this are aired and people like you, not politicians or scientific experts but citizens, express their concern."