We looked at some of these eco-friendly celebrities, who have adopted the concept of hybrid and electric cars, eco changes, lowering their carbon footprint and being overall very progressive in their "green thinking". Some successfully, while others ... not so much.

Tom Hanks

The initial concept of hybrid cars wasn't a good enough solution for one of the best paid actors in the world. While hybrid cars were a step in the right direction, they still used gas, which is why this Hollywood star switched to an electric car before the world even knew what electric cars were. Years ago, he even made a YouTube video with him driving around Los Angeles and explaining how his electric Scion xB (or the remodeled electric version of it, anyway) worked.

Jennifer Aniston

It was in 2007, during Al Gore's events for the Live Earth project, that Jennifer Aniston told the media about her changed showering regime – one she adopted after finding out that with just two minutes of showering, we use as much water as a person in Africa uses in a whole day. That is why Aniston decided to cut down her showering time to just three minutes! Furthermore, she revealed that she also brushes her teeth while showering in order to further reduce the consumption of water. Smart? Some dental hygienists might not be too pleased with this solution, seeing as it takes at least 2 minutes to properly brush your teeth, while others pointed out that she'd use much less water if she would simply shower quickly and then brush her teeth at the sink, where a lot less water is used.

Leonardo DiCaprio

Always on the frontlines of important movements, it came as no surprise when Leo DiCaprio became an important figure in many eco projects of the last decade. His actions include him lending his talent to important media messages, amongst others an intriguing documentary The 11th Hour, which he wrote, co-produced and narrated and his cooperation with Discovery Channel, where he became part of a reality show about green rebuilding of a town in Kansas that was ruined by a tornado. But his green actions extend into his real life as well. He's a proud owner of a Toyota Prius hybrid, while his bathroom hosts an eco-friendly toilet. We have to get us one of those!

Sheryl Crow

Deemed by some as the The Queen of Green, Sheryl Crow has taken big steps to make her concerts and tours as eco-friendly as possible. Her instructions on how they must set up the venues (as well as handle the whole tours!) in order to "minimize the overall environmental impact" includes two and a half pages, aptly named "environmental portion", of various steps that need to be taken. This includes use of only biodegradable cups by the caterers, food made for her and the staff should be organic, while ingredients (if at all possible) purchased from local suppliers, use of recycled toilet paper and napkins and many more. She even suggests the promoters to switch traditional light bulbs for compact fluorescent bulbs in offices, dressing rooms and other areas.

But how green is too green? On her Stop Global Warming campaign in 2007, when she visited several college campuses around The States, she urged the students to only "use one square of toilet paper". We gave it a little thought and came to a consensus that the only time just one sheet of toilet paper is enough, is ... never.

George Clooney

It was clear that the handsome Hollywood star went "full green" when he was amongst the celebrities featured in the first "green" issue of Vanity Fair magazine, along with Julia Roberts, Al Gore and Robert F. Kennedy. He owns two electric cars (but realizes he's also part of the problem since he's flown on private jets many times), one of which is a Tango, which he traded his BMW for and so became the first American who purchased that particular electric vehicle.

After his role in Syriana, a fictionalized scenario about the corruption in the oil industry, Clooney decided that just "talking the talk" is not enough – he has to "walk the walk". He then became actively involved in a campaign to decrease America's dependency on foreign oil called Oil Change.