And it was all thanks to Ellen DeGeneres, who will air a clip of the adorable meet-and-greet on The Ellen DeGeneres Show Friday. But you can watch it below right now.
Sophia Grace, 10, and Rosie, 7 – who just nabbed their own NBC comedy series – scored some hands-on choreography tips from Spears, who walked them through a quick snap-and-pop routine. (Those gals know how to work it!)
But the highlight came when the child stars, hand in hand with Spears, took the singer around a corner of the studio to reveal a surprise birthday bash, complete with cupcakes, party favors and ... tea. (Hey, Sophia Grace and Rosie are British, after all.)
The duo even presented Spears with her own blinged-out tiara, which, appropriately, came with its own built-in mic.
When Sophia Grace asked the singer what her birthday wish was, Spears replied, "To have four vacations a year."