Pop mom Britney stopped by Madonna's L.A. concert for an unannounced duet -- and Ms. Spears keeps the surprises coming, revealing she'll be across the pond for Thanksgiving!

According to BritneySpears.com, the "Womanizer" singer is set to appear on the French music talent show, "Star Academy" on November 28 -- the day after families across America will be giving thanks and chowing down.

Britney jetted off to Louisiana this weekend with her tots, presumably to visit her family in her hometown.