SuperFan orders SexyBack: SING, Justin!

Ol’ SexyBack JUSTIN TIMBERLAKE – waiting outside Chateau Marmont for valets to bring his car – suddenly had his sexy back to the wall when a middle-aged femme fan bustled up with a teen daughter in tow and asked to video him warbling “Happy Birthday” to her other (absent) daughter.

Grinning good-naturedly, JT crooned it into the woman’s camera phone – only to be asked: “One more time, please!”

Explained Mrs. Pushy: “That was good, but you didn’t say her name right.” Said My Marmont Spy: “Justin, actually amused, sang it again – but the woman, still not thrilled, ordered a third retake. At that point, security guards approached to intervene, but Justin – suddenly finding the whole thing hilarious – told guards it was okay, and performed TAKE #4!”

Beamed Pushy Momma: “That was…pretty good!” Said Justin: “My pleasure!” – and climbed into his car as Teen Daughter, covering her eyes in embarrassment, gasped: “MOM!”