Leader of the Pack

Justin Timberlake was top cat at Wednesday's Alpha Dog premiere.

But noticeably absent was longtime girlfriend Cameron Diaz. Although the status of their relationship has been the subject of tabloid and celebrity blog reports recently, Timberlake's camp would shed no light on the topic.

"There will be no statement," publicist Ken Sunshine said. He neither confirmed nor denied a split.

Reporters opted not to annoy the star with questions about Diaz. And when CNN asked the SexyBack singer to comment on his ex, Britney Spears, he excused himself.

The focus instead turned to JT's acting debut. In the movie, due Jan. 12, Timberlake plays one of several suburban twentysomethings involved in a teen's kidnapping.

"The biggest challenge for me was making sure the other actors knew I was going to come in, be humble and do the work," Timberlake said.

Sharon Stone, who plays the kidnapped boy's mother, lavished Timberlake with praise.

"We see people who want to cross over, but don't cross over with discipline and respect — like any actor saying, 'Oh, I think I'll be a singer or a fashion designer,' " she said. "But he's behaving in a way that makes us take him seriously."

Behaving responsibly is the main message Stone hopes audiences, particularly parents, will take away from the film. As mother to sons Roan, 5, Laird, 1, and Quinn, 6 months, Stone said: "It should teach us that we have a responsibility to care for all children. We have to behave decently and kindly so they respond decently and kindly."

Before jetting off to San Diego for his concert tour, Timberlake was all smiles at the after-party as he entertained guests.

The singer/actor also created a party mood during filming as a diversion from the disturbing plot.

"Justin danced Thriller on set," said Anton Yelchin, who plays the kidnap victim.

And Emile Hirsch, who plays the kidnappers' ringleader, noted Timberlake's fondness for "singing in the car on the way to the set. It was like getting to sit front row at one of his concerts."

Hearing those stories made Timberlake blush. "I wanted to be like everyone else," he said. "I guess my gift to them was that I just shut up."