Justin Bieber turns 18 today! To celebrate the milestone, the teen pop sensation stopped by The Ellen DeGeneres Show, where his manager presented him with an eco-friendly Fisker Karma car. Bieber's reaction: "That's mine? That's amazing!" He then took to Twitter to ask his fans to give back by donating to Charity: Water, a nonprofit organization that provides clean drinking water to people in developing nations. "I want to use my bday to help others. if u want please donate $18 to @charitywater on my 18th bday!" he wrote. Beliebers, leave your birthday wishes in the comments!