Selena Gomez and Justin Bieber ramped up the PDA on the set of his new music video on Saturday with some sizzling action.

The 18-year-old pop star was filming scenes for his new song Boyfriend -- with a Selena look-alike no less -- when the real Gomez came for a visit and the pair could barely keep their hands off of each other in between takes.

It's been four months since we've heard anything from Mariah Yeater about her claim that Justin Bieber fathered her baby. But Biebs himself brought the story back to life Saturday afternoon with a surprising tweet.

"Dear mariah yeeter...we have never met...so from the heart I just wanted to say," Bieber tweeted and he then linked to a snippet of Sacha Baron Cohen as Borat saying, "You will never get this."

Justin Bieber tells V Magazine that while "people need to know I'm not a kid anymore," he admits he's not "completely grown-up" either.

"I'm still learning," said the pop star, who turns 18 on March 1. "I'm not going to try to conform to what people want me to be, or go out there and start partying, have people see me with alcohol. I want to do it at my own pace.”

Unlike good girl-turned-bad Rihanna, don’t expect the teen to start getting into topic matter to reflect values those his age might embrace.

"I don't want to start singing about things like sex, drugs and swearing,” he said. “I'm into love, and maybe I'll get more into making love when I'm older. But I want to be someone who is respected by everybody."

Mariah Yeater, the 20-year-old California woman who claims Justin Bieber sired her 5-month-old son, is holding steadfast to her story that the pop singer is the child's father.

When asked by the Chicago Sun-Times on December 14 whether or not ex-boyfriend Robbie Powell -- who was arrested November 26 on drug and burglary charges -- is the real father, Yeater replied, “Yes, I know him.”

But then insisted, "He is not the father, and he’s locked up and out of the picture.”

PHOTOS: Justin Bieber Snaps Pics Of Sexy Selena Gomez In Cabo

Robbie Powell is reportedly the “real father” of Mariah Yeater’s baby — although she’s claiming Justin Bieber is the dad — and RadarOnline.com has exclusively learned that Robbie was arrested in San Diego over the Thanksgiving weekend.

According to the arrest report, Robbie was busted on November 26 at 11:41 p.m. for drug and burglary charges. The 23-year-old was charged with four felonies and one misdemeanor — possession of a controlled substance (methamphetamines), possession of drug paraphernalia, and three charges of commercial burglary.

Robbie is not eligible for release and currently remains in the San Diego Central Jail where he has a combined bail amount of $7,000. He has two court dates set for later this week.

Selena Gomez is making surprise baby news on Friday. The singer, 19, stunned her fans with the announcement that her family is expanding.

But no, she and Justin Bieber aren't expecting. It's her mother who is pregnant!

"Momma and Brian are finally letting me share the news...My mommy's carrying my baby brother or sister:)  I'm the happiest girl in the world!!" Selena tweeted.

PHOTOS: Bieber & Gomez Immortalized In Wax

Selena's parents divorced when she was just five.  In 2006, her mother Mandy married Brian Teefey, this will be their first child together.

Selena has stuck by boyfriend Bieber, 17, throughout the scandal brought by Mariah Yeater who claimed he fathered her baby.

PHOTOS: Selena Gomez Looks Sexy In Paris With Justin Bieber

Biebs has always denied the allegation and as RadarOnline.com reported on Monday, he's now taken a DNA test to prove the claim is false.

Justin Bieber appears on The Late Show with David Letterman in a pre-taped interview Wednesday night, and addresses his ongoing scandal involving 20-year-old California woman Mariah Yeater, confirming he recently took a paternity test to see if he’s the father of her 4-month-old boy.

Letterman asked the pop star about the fiasco, adding it made him "see red.

"I was so angry," said Letterman, who's been targeted by stalkers and an extortionist throughout his vaunted career. "I can smell a weasel."

Justin Bieber has taken a DNA test to prove that he isn't the father of Mariah Yeater's son, RadarOnline.com has confirmed.

As RadarOnline.com and Star magazine previously reported, the 20-year-old woman filed a bombshell paternity suit against Bieber, alleging he is the father of her three-month-old baby.

Yeater filed court papers saying that her sexual encounter with the Baby hit-maker occurred on October 25 of last year, after he performed to a sold-out crowd at L.A.'s Staples Center.

The romance between Justin Bieber and Selena Gomez has been immortalized -- in wax.

The Madame Tussauds in New York unveiled a pair of wax statues of the young superstars Thursday, decked out in a holiday scene, and RadarOnline.com has the photos.

PHOTOS: Bieber & Gomez Immortalized In Wax

Justin and Selena have been dating for more than a year and went public with their romance in February at Vanity Fair’s Oscar awards after-party.

And the two have stuck together in the midst of a paternity lawsuit thrown at Justin in which a 20-year-old California woman claims he is the father of her three-month-old baby.

It's been a trying few weeks for Selena Gomez after her boyfriend Justin Bieber was named in a paternity suit, but RadarOnline.com has video of the actress saying everything will be alright.

The 19-year-old Wizards of Waverly Place beauty, appearing on Thursday's edition of The Ellen DeGeneres Show, seemed relieved in the wake of Bieber's accuser Mariah Yeater dropping her suit against the Canadian pop sensation Wednesday.

But as RadarOnline.com first learned, Yeater’s paternity lawyer, Jeffrey Leving, said they’d hired a new legal team and would be pursuing private negotiations with Bieber’s camp outside of a courthouse, including a DNA test.