The Wonder Girls with Justin Bieber (center). (Photo courtesy of www.wondergirlsworld.com)

K-pop girl band Wonder Girls opened the Valentine’s Day concert of Canadian singing sensation Justin Bieber at the Hollywood Palladium in Los Angeles, California.

The Wonder Girls sang their hit songs “Nobody” and “Tell Me” to a sold-out crowd composed mostly of—and understandably—pre-pubescent girls who were eager to see 15-year-old Beiber.

Bieber was discovered via YouTube. His debut album “My World” was released in November last year. His four singles made it to the Top 40 of Billboard’s Hot 100 chart.

His second album, “My World 2.0” will be released in March.

In a review of Bieber’s concert, the Los Angeles Times music blog “Pop & Hiss” described Bieber as the "new David Cassidy."

“For those who don’t spend much time around teenagers, Bieber is something of a new David Cassidy for the era of Auto-Tune. He has the classic prerequisites of stardom in this demographic: apple cheeks, stunning orthodontics, the sly pout of troublemakers from Tom Sawyer on forward,” wrote the blog’s August Brown.

The Wonder Girls’ performance was first of the last two appearances with member Sunmi who will be leaving the group in March to continue her high school education in South Korea. She is to be replaced by JYP Entertainment trainee Hae Lim.

Sunmi will be doing her last performance with the Wonder Girls at the Pop-Con on Feb. 20 at Nassau Coliseum in Uniondale, New York.

The Pop-Con is an all-day music festival experience, targeted specifically for the Tween market. It has multiple stages, various vendors and games with the amenities of a family-friendly convention environment.

Featuring over half-a-dozen musical artists, skateboarders and young pop icons, Pop-Con aims to be the "pop event with the stars the kids want to see,” according to the event organizer.

The Wonder Girls will be performing at the Pop Con alongside Bieber, Selena Gomez and the Scene, Sean Kingston and other singers.