Justin Timberlake and Jessica Biel made a rare appearance together Saturday at a Las Vegas rally for Barack Obama. Timberlake performed an off-the-cuff riff, singing "Vote in a Box," a spoof of his infamous raunchy Saturday Night Live sketch, a campaign source tells Usmagazine.com. "Me and Jess, we're here as Americans. We're here as humans because this is something we had to do," Timberlake told the crowd at the Clark County Government Center amphitheater, according to the Las Vegas Review-Journal. He added, "We've never publicly endorsed before. But we've never been so inspired by one person." (A source tells Us that Timberlake's mother, Lynn, helped him write his opening remarks.)

Noting that the next president's Supreme Court appointments could determine the future of legal abortions, Biel told the crowd, "Nobody should be able to say what you can do with your body." Joked Timberlake, "I give Jess the right to choose where we go to eat all the time. The funny thing is, what the woman chooses is usually right." "Brownie points for you," Biel kidded back. Teased Timberlake, "I know where my bread is buttered."

Felice Garcia, a 21-year-old college student who attended the rally, told the Review-Journal she was impressed Timberlake took time out to attend the rally. "I really respect him for that," she said. "He obviously cares about this."