Disney Channel sweethearts Zac Efron, 23, and Vanessa Hudgens, 21, have been tween Hollywood's golden couple since 2006, when the High School Musical costars began dating. But on Dec. 13, E! Online revealed the two broke up. "They were together for so long. It just ran its course," a source said of the couple's four year relationship, adding there was "no third party involved."